Xcode4 userguide Apple

Contents

About Xcode 12
At a Glance 12
Get Oriented to Xcode Organization and Features 13
Design the Look and Behavior of Your App 13
Debug and Refine Your Code 13
Safeguard Your Projects Using Source Control 13
Distribute Your App to App Testers or Publish it on the App Store 14
See Also 14

Get Oriented 15
Contextual Help: Your Shortcut to Answers 15
The Workspace Window: Where You Get Most of Your Work Done 16
Open Work in Tabs and Windows 18
Edit and View Many Types of Data 19
Find Information to View or Edit 31
Find Information that Supplements the Editor 47
Check on the Progress of Xcode Tasks 50
The Organizer Window: Managing Projects, Devices, and Documentation 51
Browse and Bookmark Documents 51
Browse for Task-Based Help 54
Work with Your Source Control Repositories 54
Organize Your Projects and Devices 55
Take a Snapshot of Your Project 55

Start a Project 56
Click New Project in the Xcode 4 Startup Screen to Create a Standalone Project 56
Create a Git Repository For Your New Project 58
Select Options While Creating a New Project 58
Create a Workspace to Work with Multiple Related Projects 59
Check Out a Working Copy from Your Source Control Repository 63
Modernize Your Project 63
Add Automatic Reference Counting 64
Close a Project or a Workspace 65

2012-09-19 | © 2012 Apple Inc. All Rights Reserved.

2

Contents

Configure Your Project 66
Add Build Configurations 66
Set the Basic Build Settings 69
Add Build Rules 72

Edit User Interfaces 76
Create Your User Interface 76
Display Your User Interface Objects 78
Connect to Other Files Using Placeholder Objects 79
Select Hidden Objects in an Interface File 82
Lay Out User Interface Controls Using Content-Driven Rules 84
Add New Constraints 87
Allow Objects to Maintain Their Intrinsic Content Size 90
Override Automatic Constraints 91
Set Priorities to Resolve Potential Conflicts 92
Design the User Interface of Your iOS App with Storyboards 92
Create User Interface Classes 97
Add a New Nib File 98
Add a Custom View 102
Add a New Controller 103
Simultaneously Design and Implement User Interface Objects Using Multiple Editors 117
Manage Connections Between User Interface Objects 106
Make Connections Directly Between IB Objects and Your Code Files 107
Add Outlets and Actions to Classes Programmatically 110
Use the Inspector or the Connections Panel to Make Connections 111
Configure Connections Between Model and View Objects 114
Create and Configure a Binding with the Bindings Inspector 115
Create a Binding by Dragging Directly to Your Header File 116
Key Paths Are Dependent on Your Data Model 117
Configure the Binding Attributes to Customize the Binding 118
Bind to Objects in a Custom Tree Data Structure 118
Bind to Your Application Preferences 119

Edit Source Code 121
Customize the Source Editor with Xcode Preferences 121
Modify Syntax-Aware Fonts and Text Colors 121
Set Your Text-Editing and Automatic Indentation Preferences 125
Enter Code Quickly and Accurately with the Help of the Source Editor 125
Speed Up Typing with Code Completion 125
Balances Delimiters Automatically 128


3

Contents

Have Fix-it Flag Errors as You Type 129
Find and Display Related Content 130
Open a FIle Quickly 130
Split the Editor Area to Display Related Content 132
Customize Keyboard Shortcuts to Determine Where a File’s Contents Are Displayed 134
Jump to a Symbol’s Definition 136
Find Related Items with the Jump Bar 138
Find Related Content Automatically 138
Use Assistant with Interface Builder and Data Models 140
Incorporate Other Source Editor Features into Your Workflow 141
Examine the Structure of Your Code with Code Folding 141
View Preprocessor or Assembly Output 143
View Documentation for a Symbol Using Quick Help 144
Automate Extensive Changes in Your Files 147
Incorporate Files and Code from the Xcode Libraries 148
Use Inspectors to View and Enter Data 152

Build and Run Your App 153
Create, Edit, and Manage Schemes 178
Specify Which Targets Are Built for Each Type of Action 155
Rename or Reorganize Your Schemes 156
Configure and Execute Actions 158
Run Your Application to Debug It 158
Run Unit Tests to Find Regressions 163
Profile Your Application to Find Problems and Optimize Your Code 168
Perform Static Analysis To Find Semantic Problems 169
Create an Archive for Sharing or Submitting Your Program 169
Initiate an Action 170
Customize Your Build and Run Workflow 172
Fine-Tune Your Builds 176
Control the Order in Which Xcode Builds Your Products 178

Debug Your App 180
Select a Debugger 180
Find Coding Mistakes 181
Locate Possible Semantic Problems 181
Locate and Display Build Issues 183
Manage Breakpoints 188
Add and Activate Breakpoints 188
Edit Breakpoints 190


4

Contents

Share Breakpoints 192
Set Preferences for Breakpoint Behavior 193
Customize the Debug Area 194
The Variables Pane 194
The Console Pane 195
Control Program Execution 195
Step Through Code with the Debug Bar 195
Set a Location in the Debug Bar 196
Step Through Code in the Source Editor 196
Suspend a Thread 197
Set Xcode Window Behavior 199
Examine Threads, Stacks, Variables, and Memory 200
Capture OpenGL ES Frames 206

Make Projectwide Changes 215
Replace Text Strings 215
Replace All Instances of a Text String 216
Replace Selected Instances of a Text String 218
Customize the Search 219
Improve Your Code’s Structure Through Refactoring 221
Select the Source Code to Refactor 221
Preview the Changes Before Executing the Operation 222
Run Unit Tests Before and After Refactoring 222
Choose a Refactoring Operation 223

Manage Your Devices 225
Set Up Your Device 226
Provision a Device 226
Restore or Install a Version of iOS on a Device 229
Run Your Application On the Device 230
Remove an Application from a Device 230
Download Your Application’s Data for Analysis 232
Capture and Use Screenshots from a Device 234
Set a Screenshot as Your iOS Application’s Launch Image 235
Export a Screenshot to Your File System 237
Identify Small UI Changes by Comparing Screenshots 238
Transfer Your Developer Profile to Another Computer 239

Save and Revert Changes to Files 244
Save when Editing 244


5

Contents

Revert to the Last Saved Version 244
Undo Changes Incrementally 246
Unlocking Files 247
Use Snapshots and SCM for Projectwide Change 249
Snapshots Archive Projectwide Changes to Documents and Configuration 249
SCM Repositories Manage Overall Change as Your Project Develops 249

Save and Revert Changes to Projects 251
Take a Snapshot of Your Project 252
Keep Track of Changes with Source Control 253
Why Use Source Control? 277
Choose Git or Subversion 254
Learn SCM Terminology 254
Manage Your Repositories 256
Find SCM Commands 258
Keep Track of Your Files’ SCM Status 260
Work with Git and Subversion 261
Set Up Git Version Control When You Create a New Project 261
Add Git or Subversion Version Control to an Existing Project 261
Clone or Check Out a Copy of a Project to Use Locally 264
Add an Existing SCM Working Copy of a Project to Xcode 265
Create a Branch to Isolate Risky Changes 265
Clone a Specific Branch 268
Add a Folder to a Subversion Repository 270
Commit Files to Add Them to a Repository 271
Reconcile Different Branches 272
Update Your Working Copy from a Remote Repository 273
Send Your Working Copy to the Remote Git Repository 277
Save Internal Project Files in Repositories 278
Compare Revisions 278
Select Specific Revisions 279
Review Individual Changes 280
View All Revisions Chronologically 281
Distribute Your Program 282

Distribute Your App 284
Archive Your App 287
Validate Your App 285
Distribute Your iOS App 287
Distribute Your Mac App 289


6

Contents

Document Revision History 291


7

Figures and Tables

Get Oriented 15
Figure 1-1
Figure 1-2
Figure 1-3
Figure 1-4
Figure 1-5
Figure 1-6
Figure 1-7
Figure 1-8
Figure 1-9
Figure 1-10
Figure 1-11
Figure 1-12
Figure 1-13
Figure 1-14
Figure 1-15
Figure 1-16
Figure 1-17
Figure 1-18
Figure 1-19
Figure 1-20
Figure 1-21
Figure 1-22
Figure 1-23
Figure 1-24
Figure 1-25
Figure 1-26
Figure 1-27
Figure 1-28
Figure 1-29
Figure 1-30
Figure 1-31
Figure 1-32
Figure 1-33

Contextual help 15
A newly opened Xcode window 16
The project contents in the Xcode project navigator 16
The utility area 17
The debug area 18
The source editor 21
Target information in the project editor 38
Build settings 23
Quick Help for key values 24
The data model editor 28
The mapping model editor 29
Interface Builder 30
Editor selector buttons 31
The navigators 31
A folder and groups in the project navigator 33
The project navigator filtered to show only .m files 36
Project navigation 36
The jump bar in Interface Builder 38
The related items pop-up menu 39
The Find Options dialog 42
The issue navigator 43
The breakpoint navigator 44
The debug navigator and associated editor and debug areas 45
Viewing a log 46
The utility button 47
Data model inspectors 48
Interface Builder inspectors 48
The library pane 49
The activity viewer 50
The activity pop-up window 50
Issues in the activity viewer 50
The Organizer button 51
The documentation navigator 51


8

Figures and Tables

Figure 1-34
Figure 1-35

The bookmarks navigator 52
Xcode help start screen 54

Start a Project 56
Figure 2-1
Figure 2-2
Figure 2-3
Figure 2-4
Figure 2-5

The option to add source control when creating a project 58
Options for a new project 59
A shortcut menu for a workspace 62
Modernization in the Issue navigator 63
Updates dialog 64

Configure Your Project 66
Table 3-1
Table 3-2

Mac OS X project editor Summary pane settings 70
iOS project editor Summary pane settings 72

Edit User Interfaces 76
Figure 4-1
Figure 4-2
Figure 4-3
Figure 4-4
Figure 4-5
Figure 4-6
Figure 4-7
Figure 4-8
Figure 4-9
Figure 4-10
Figure 4-11
Figure 4-12
Figure 4-13
Figure 4-14
Figure 4-15
Figure 4-16
Table 4-1

Interface Builder in the workspace window 77
Icon view for placeholders and objects in Interface Builder 78
Auto Layout 85
User constraint 88
Button set to maintain its intrinsic content size 90
Automatic constraints 91
User-added trailing constraint 91
User-added leading constraint 92
The Use Storyboard option 93
View controllers in the object library 94
Creating a storyboard 95
Attributes inspector for a segue 96
Storyboard for an iOS Application 97
Interface Builder and Assistant 106
Making a connection to source code from Interface Builder 107
Help articles in Interface Builder 110
Auto Layout constraints 88

Edit Source Code 121
Figure 5-1
Figure 5-2
Figure 5-3
Figure 5-4
Figure 5-5
Figure 5-6

Fonts & Colors preferences 122
Code completion 126
Quick Help for code completion 128
Placeholders in code completion text 128
The Assistant button 132
General preferences 134


9

Figures and Tables

Figure 5-7
Figure 5-8
Figure 5-9
Figure 5-10
Figure 5-11
Figure 5-12
Figure 5-13
Figure 5-14
Figure 5-15

The Single Assistant navigation chooser dialog 135
The navigation chooser dialog 136
The assistant editor used with a data model 140
The focus ribbon in use 142
Preprocessor output 143
Generated output in Assistant jump bar 144
The Quick Help window 145
A file template information pop-up window 149
The File inspector 152

Build and Run Your App 153
Figure 6-1
Figure 6-2
Figure 6-3
Figure 6-4
Figure 6-5
Figure 6-6

The Scheme pop-up menu 153
The manage schemes dialog 157
The scheme editor Run pane 158
Choosing a location in the scheme editor 163
Behaviors preferences 172
Project editor help topics 176

Debug Your App 180
Figure 7-1
Figure 7-2
Figure 7-3
Figure 7-4
Figure 7-5
Figure 7-6
Figure 7-7
Figure 7-8
Figure 7-9
Figure 7-10
Figure 7-11
Figure 7-12
Figure 7-13

The issue navigator 183
The debug area 194
Choosing a location in the debug bar 196
Xcode In Front window mode while the executable is running 199
Xcode In Front window mode while the executable is paused 200
Enabling OpenGL ES frame debugging 207
Frame capture button 208
OpenGL ES frame capture 209
Controls for stepping through draw calls 210
Shortcut menu 211
Wireframe view 212
Frame capture with two Assistant panes 213
Vertex Array Object detail 214

Make Projectwide Changes 215
Figure 8-1
Figure 8-2

Search and replace using the search navigator 215
The refactor preview dialog 222

Manage Your Devices 225
Figure 9-1

Devices organizer 225


10

Figures and Tables

Save and Revert Changes to Files 244
Figure 10-1
Figure 10-2
Figure 10-3
Figure 10-4

Workspace window with in-memory changes to files 245
Undo Typing command 246
File could not be unlocked 247
Locked file indicators 248

Save and Revert Changes to Projects 251
Figure 11-1
Figure 11-2
Figure 11-3
Figure 11-4
Figure 11-5
Figure 11-6
Figure 11-7
Figure 11-8
Figure 11-9
Figure 11-10

The Snapshots settings dialog 252
Snapshots listed in the Organizer window 253
The repositories pane in the Organizer window 256
The Source Control submenu of the File menu 259
The Source Control submenu of the project navigator shortcut menu 259
Repositories organizer buttons 259
Source control badges in the project navigator 260
A scheme in the commit dialog 278
Comparing two revisions of a file with the version editor 279
The archives organizer 283


11

About Xcode

Xcode is the integrated development environment (IDE) designed for developing iOS and Mac apps. The Xcode
IDE includes editors used to design and implement your app, such as a source code editor and a user interface
editor. Xcode also supports multiperson development using source control management (SCM) systems. As
you write source code, Xcode can show you mistakes in both syntax and logic, and even suggests fixes.
Xcode features a single window, called the workspace window , that holds most of the data you need.
Toolbar
Navigator
selector bar

Inspector
selector bar

Jump bars

Breakpoint gutter

Inspector pane

Focus ribbon
Editor
area

Navigator
area

Utility
area

Library
selector bar
Library pane

Debug
area

Filter bar

Debug bar

Read this guide to get started using Xcode.

At a Glance
Xcode has many features to make your job easier.
●

Single-window interface. You perform most of your development workflows in one window (you can
have multiple workspace windows and multiple tabs per window).


12

About Xcode
At a Glance

●

●

●

●

Graphical user interface design. With the Xcode user interface editor, called Interface Builder, you specify
most of the details of your app’s user interface, such as the layout of the user interface controls, and their
connection to your app’s business logic and the data it manages, using a powerful and intuitive graphical
user interface. Interface Builder works closely with other editors, such as the source code editor, to take
you from design to implementation as fast as possible.
Assisted editing. When you need to work on different aspects of the same component, such as user
interface layout and the implementation of the user interface functionality, you can use multiple editors
that open the content you need when you need it. For example, when you work on an implementation
file in the primary editor, Xcode can open the corresponding header file in a secondary editor pane.
Automatic error identification and correction. Xcode checks the source code you type as you type it.
When Xcode notices a mistake, the source code editor highlights it. You can then find out details about
the error and ask Xcode to fix it for you.
Source control. You can safeguard all your project files in Git and Subversion source code repositories.

Get Oriented to Xcode Organization and Features
Xcode is a powerful tool. But, as it’s true with any complex product, you need to know essential concepts and
workflows before you can start developing products efficiently.
Relevant Chapters: "Get Oriented" (page 15), "Start a Project" (page 56).

Design the Look and Behavior of Your App
Two of the most important tasks you perform while you develop your app is designing its user interface and
writing the business code that implements your app’s unique functionality.
Relevant Chapters: "Edit User Interfaces" (page 76), "Edit Source Code" (page 121).

Debug and Refine Your Code
Xcode provides a debugging environment that you can customize to automatically bring forward the parts of
your code in which you are interested the most.
Relevant Chapters: "Debug Your App" (page 180), "Make Projectwide Changes" (page 215).

Safeguard Your Projects Using Source Control
Xcode provides easy local backups with snapshots and the ability to work in a team using SCM.
Relevant Chapter: "Save and Revert Changes to Projects" (page 251).


13

About Xcode
See Also

Distribute Your App to App Testers or Publish it on the App Store
Share your app with other members of your development team or app testers, or publish it on the App Store.
Relevant Chapters: "Distribute Your App" (page 284).

See Also
Before developing your iOS or Mac app, you must be familiar with the design and coding practices required
by your target platform. See Developing for the App Store to learn the basics of app development.


14

Get Oriented

Once you’ve got your projects open in Xcode, you can start writing code. This chapter describes where to find
the most commonly used features of Xcode. The remaining chapters describe the use of some of these features
in more detail.

Contextual Help: Your Shortcut to Answers
In addition to being listed in the documentation browser in Xcode ("Browse for Task-Based Help" (page 54)),
many help articles are available from shortcut menus throughout the application. Control-click in any of the
main user-interface areas in the workspace or Organizer window to see a list of help articles available for that
area. Figure 1-1 shows contextual help for the source editor. If there are more articles than can be listed in the
shortcut menu, choose Show All Help Topics; the help opens in the Organizer window (Figure 1-35 (page 54)).
You can use this facility to find information about a specific task that you’re trying to accomplish, or just to
learn what tasks can be performed using that area of Xcode.
Figure 1-1

Contextual help


15

Get Oriented
The Workspace Window: Where You Get Most of Your Work Done

Before going any further, you need to get oriented to the Xcode workspace window (Figure 1-2).
Figure 1-2

A newly opened Xcode window

The left side of the window is the navigator area, opened to the project navigator in the figure. The project
navigator shows the contents of your project or workspace. Figure 1-3 shows some of the groups and files in
a project.
Figure 1-3

The project contents in the Xcode project navigator


16

Get Oriented

The right side of the window in Figure 1-2 (page 16) is the editor area. You can edit many types of information,
including source code, property lists (plists), Core Data models, and user interface (nib or storyboard) files, and
you can view many more.
To supplement the information in the editor area, you can open a utility area at the right of the workspace
window (Figure 1-4), which includes inspectors and libraries. Use the view selector (
to open and close the navigator, debug, and utility areas.
Figure 1-4

The utility area


17

) in the toolbar

Get Oriented

When you are running code, the debug area opens (Figure 1-5). When you stop at a breakpoint, the debug
navigator opens as well.
Figure 1-5

The debug area

Open Work in Tabs and Windows
For fast switches between different editors or files, you can add tabs to the Xcode workspace window, or you
can open additional windows. To activate tabs, choose View > Show Tab Bar, or add a new tab by choosing
File > New > New Tab. Choose File > New > New Window to open a new workspace window. Each tab or
workspace window can be customized independently of the others. For example, you can use one window to
debug and another to edit source code. If you open the same file in two tabs or two windows, the changes
you make in one tab or window are reflected in the other.
Tabs can be reordered, closed independently, or dragged out of the tab bar to create a new window, just as
they can in Safari. You can use items in the Window menu (or their keyboard equivalents) to move between
tabs. You can also give a tab a name for use in Behaviors preferences (see "Customize Your Build and Run
Workflow" (page ?)).
Xcode remembers the windows and tabs you had open when you last closed a workspace and reopens them
in the same configuration.


18

Get Oriented

Edit and View Many Types of Data
Xcode includes editors for many file types, including:
●

Source code

●

Project and build settings

●

Property list (plist) files

●

Rich text (rtf ) files

●

Core Data models

●

Core Data mapping models

●

User interface (nib) files

●

AppleScript files

●

Scripting dictionary files

There are viewers that can display graphics, videos, and a variety of other file types.
The use of each of these editors is briefly described in this section. Control-click in any of the editors to get a
list of help articles that further describe the use of the editor (Figure 1-1 (page 15)).

Select Any File
To open any of the editors or viewers, select a file in the project navigator. The editor or viewer for that file
type opens automatically in the editor area of the workspace window. Any file for which Xcode does not have
an editor is displayed using Quick Look. (Quick Look is also used by the Finder. In the Finder, select a file and
press the Space bar or choose Quick Look from the File menu to see it in use.)
Each document-type editor has custom commands in the Navigate and Editor menus to act on the information
in that type of document. Note that the Navigate menu—like several of the menus in Xcode—shows different
menu items when you hold down the Option, Shift, or Option and Shift keys.

Edit in Hexadecimal Format
You can view most file types in hexadecimal format by Control-clicking the file in the project navigator and
choosing Open As > Hex from the shortcut menu. Some file types that are not editable in the default viewer,
such as image files, can be edited in hexadecimal format.
You can edit the hexadecimal code directly, or you can edit in the plain text column. Editing either updates
the other.
When the hex editor has focus, you can use the Editor menu to customize its display.


19

Get Oriented

View and edit a file in its binary format by opening it in the hex editor.

To open a file with the hex editor . . .
1.

Control-click a file in the project navigator.

2.

Choose Open As > Hex.

The hex editor has three areas:
●

●

●

On the left, the line numbers
In the center, the hexadecimal representation of the bytes in the file, 32 bytes per line, one byte per
column
On the right, the plain-text (ASCII) representation of those bytes

From the Editor menu, you can hide the line numbers or the plain-text representation. You can also choose
to display the byte codes in groups of 2, 4, 8, 16, or 32.
The screenshot shows an image file in the hex editor.


20

Get Oriented

Write, Edit, and Debug Source Code
The Xcode source editor has many features to help you develop source code. Among other features, you can
write and edit source code (see "Edit Source Code" (page 121)), set and enable or disable breakpoints (see
"Manage Breakpoints" (page 188)), and control program execution during a debugging session (see "Control
Program Execution" (page 195)). Control-click in the source editor to see a list of help topics describing features
of the editor and tasks you can accomplish (Figure 1-1 (page 15)).
Figure 1-6

The source editor


21

Get Oriented

Note: When you edit a file in Xcode, the file’s icon is shaded in the project navigator to indicate
that there are unsaved changes. You can save the file, or if you quit Xcode or build the project, Xcode
automatically saves all changed files for you by default (you can change this behavior in the General
pane of Xcode preferences). To ensure you can return to a known state before you build your project,
create a snapshot (see "Take a Snapshot of Your Project" (page 55)).

Edit Build Settings
When you click the project icon in the project navigator, the project editor appears to the right of the project
navigator, displaying project and target information. Figure 1-7 shows some of the target information in the
project editor.
Figure 1-7

Target information in the project editor

Click the various buttons and icons in the project editor to see the information that’s in there.


22

Get Oriented

You can choose to view basic build settings or all settings. The values of build settings can be set at the default,
project, or target level. You can edit a build setting at the project or target levels. Click the Levels button to
see all the levels of build settings simultaneously, as in Figure 1-8. The setting that takes precedence is
highlighted in green and shown in the Resolved column. If you have changed or customized a setting, it’s
shown in boldface. Click the Combined button to see just the resolved build settings.
Figure 1-8

Build settings

See "To add a new build configuration" (page 66) for more information on using build settings.

Edit Keys and Values
In addition to the Info.plist file required for every application, the property list editor opens a variety of
other property list file types.
To edit a key or a value, double-click the item and type a new string into the text field. In some cases, a pop-up
menu is available, indicated by small vertical arrows. Click the arrows to see the choices.
You can add a new property or you can add a new child property for an array or dictionary. The property list
editor warns you if you attempt to add a key that already exists in the file.
Add a new property to a property list using the property list editor.

To add a property to a property list . . .
1.

In the property list editor, hold the pointer over an entry and click the Add (+) button.

2.

Choose a key name from the pop-up menu.


23

Get Oriented

3.

Choose a value from the pop-up menu in the Value column or enter a value.

If you are adding a property that is an array or dictionary, click the disclosure triangle and press Return to
add a child property.
You can add a property with a name that is not in the pop-up menu. To do so, type the key name in the
field at the top of the pop-up menu, choose the data type from the pop-up menu in the Type column, and
enter a value in the Value column.
Click the minus (–) sign next to any item to remove it from the file.
For known property list key types, the Key column in the property list editor shows a descriptive name of the
key instead of the key’s literal text. Choose Editor > Show Raw Keys & Values to display the literal text instead.
You can also see both the name and the raw key value in Quick Help in the utility area (Figure 1-9).
Figure 1-9

Quick Help for key values


24

Get Oriented

Control-click in the editor and select Property List Type to see a list of possible file types for property lists. The
type of the current file is indicated by a dash to the left of the file name. You can use this menu to change from
the default to a specific property type.
Set the property list type when creating or editing a property list. If Xcode cannot determine the type of a
property list, you may need to set the type manually.

To set the property list type . . .
1.

Select a property list in the project navigator.

2.

Control-click in the property list editor to display a contextual menu.

3.

From the Property List Type submenu, choose a new property list type.

Property lists that share the same system-defined structure are said to have the same type. In addition to
the Info.plist file required for every application bundle, the property list editor in Xcode supports a
variety of other types. The property list type determines the list of possible keys in the key’s pop-up menu.
In the Property List Type submenu, the current type is indicated by a dash to the left of the type name.


25

Get Oriented

Edit Rich Text Files
You can write, open, and edit rich text (.rtf) files in Xcode. The editor has a user interface and feature set
very similar to those of the Mac OS X TextEdit application, but without the capability of converting the file to
other formats such as plain text or HTML. Note that Xcode opens plain text (.txt) files with the source editor,
not the rich text editor.

Design Data Models Graphically
If your project uses the Core Data framework, you can use the data model editor to implement or modify your
Core Data model (see Core Data Starting Point ).
Get a jump-start on your Core Data-based project by using one of the project templates that incorporate Core
Data.

To create a project that uses Core Data . . .
1.

Choose File > New > Project.

2.

Select the project template for your iOS or OS X product, and click Next.

3.

If the Use Core Data option appears in the project options pane, select it and click Next.
Otherwise, Core Data is not available in the selected project template.

4.

Enter the project name, and specify its location in your file system.


26

Get Oriented

5.

Click Create.

The project templates that incorporate Core Data:
●

Link against the Core Data framework

●

Add a managed object model file

●

Add code to create and locate the various parts of the Core Data stack

Use the Core Data model editor to edit the managed object model.


27

Get Oriented

Important: Not all templates offer a Core Data option.
Core Data is an advanced technology that is not required for creating simple applications.
The managed object model is a representation of the schema that describes your model objects, including
the relationships between them. Figure 1-10 shows the data model editor.
Figure 1-10

The data model editor

The top-level components area lists the entities, fetch requests, and configurations defined in the model. You
can select one or more items at a time within a single group. You use the Add Entity button to add an entity,
fetch request, or configuration. To add a fetch request or configuration, press and hold the Add Entity button
until it shows the other options. The button retains the label from the last time it was used.
The detail area shows the attributes, relationships, and fetched properties associated with the item or items
you select in the top-level components area. You can select one or more items from the same group at the
same time. There are two styles for the detail area: table and graph. You select the style using the segmented
control at the lower right of the editor area. You can use the graph style only if you select an entity in the
top-level components area. You can use either style to edit the model, however the table style is typically
better for detailed editing and inspection, and the graph style is better for visualizing your schema.
The Core Data Model inspector in the utility area displays information about the item or items you select in
the detail area. By selecting more than one property in the detail area, you can edit several properties at the
same time. For example, you can set the Attribute Type for a number of attributes simultaneously.


28

Get Oriented

Define Rules Used in Data Store Migration
If you change your Core Data model extensively enough that you need a mapping between an old store and
a new one, you can use the Core Data mapping model editor to graphically create the mapping model.
A Core Data mapping model describes the transformations needed to convert data described by a Core Data
model to another Core Data model with a different schema. The Core Data mapping model editor provides
table-based tools to create and edit a mapping model.
Tip: Before you create a mapping model, you should consider whether you can transform your data using
lightweight migration (as described in Core Data Model Versioning and Data Migration Programming Guide ).
Lightweight migration is much simpler and more efficient than mapping model-driven migration. In some cases,
you can make custom transformations by first using lightweight migration, and then performing an additional
step in code.

The mapping model editor is shown in Figure 1-11.
Figure 1-11

The mapping model editor

The entity mappings list lists all the entity mappings defined in the model. You can edit the name of the
mapping by double-clicking the text.
The property mapping tables show the attribute and relationship mappings associated with the currently
selected entity mapping.


29

Get Oriented

The new entity mapping management area allows you to add a new entity mapping to the model.
Click the Add Entity Mapping button to display a series of dialogs that you use to configure the new mapping.
If necessary, you choose the source and destination models for the entity using the corresponding pop-up
menus.
For complete flexibility, you can implement a subclass of NSEntityMigrationPolicy to set it as the custom
policy for a mapping.

Design Your User Interface Graphically
Starting with the first version of Xcode, Apple provided a separate application—called Interface Builder—for
designing graphical user interfaces. In Xcode 4, Interface Builder is fully integrated into the workspace window
as an editor. Figure 1-12 shows Interface Builder in Xcode 4.
Figure 1-12

Interface Builder

Interface Builder creates files—called nib files—that are in a proprietary format (that is, you can’t read them
with the source editor or the hex editor). For more information on the use of Interface Builder, see "Edit User
Interfaces" (page 76).


30

Get Oriented

Display Files in a Split Editor Pane
You can display two or more different views of a file, two or more different files, or two different versions of
the same file in adjacent editor panes (side by side or one above the other). You use the editor selector buttons
(Figure 1-13) to switch between the standard editor, Assistant, and the version editor. Whereas the standard
editor uses a single editor pane, Assistant and the version editor use a split-pane editor. In addition, if you
Option-click a file in the project navigator or symbol navigator pane, that file opens in the assistant editor pane
(you can change this behavior in the General pane of Xcode preferences).
Figure 1-13

Editor selector buttons

Although you can specify which file to show in each pane of the split editor, it is often helpful to let Xcode find
a related file for you. Assistant can find, for example, the header file counterpart to the source code file you’re
viewing, or the source code file used to implement the control code for an Interface Builder file. For more
information about Assistant, see "Split the Editor Area to Display Related Content" (page 132).
If your project is under source control, the version editor can compare any two versions of the file; see "Compare
Revisions" (page 278) for details.

Find Information to View or Edit
Xcode provides two ways to navigate through your project: navigators and the jump bar. Many of the navigators
include text fields for searching through the project or filtering the items in the navigator; some include buttons
to restrict the scope of items displayed. The jump bar appears at the top of the editor pane and provides an
alternate way to navigate through the files and symbols in the project. Because the jump bar is always available,
you can use it to find items in the project even when the navigator area is closed.
The navigators are shown in Figure 1-14.
Figure 1-14

The navigators
Project

Search

Symbol

Issue

Debug

Log

Breakpoint

The use of each of these navigators and jump bars is briefly described in this section. Control-click in any of
the navigators to get a list of help articles that further describe the use of the navigator.


31

Get Oriented

View the Files in Your Project or Workspace
The project navigator shows projects, groups, folders, and files:
●

●

●

●

The project or projects in your workspace window are the highest level of the hierarchy in the project
navigator. Open the project’s disclosure triangle to see the groups, folders, and files in the project. Select
the project to display the project editor, where you can view and edit project and target settings.
A group appears in the project navigator as a yellow folder icon. The group does not represent a folder
on disk. Although you can organize your project in Xcode to reflect the organization of files on disk, moving
files into and out of groups does not affect the content of the folders on disk, and moving files on disk
into and out of folders does not affect the content of the groups in the project navigator.
A folder is a reference to a folder on disk and appears in the project navigator as a blue folder icon. The
contents of the folder in the project navigator reflect the contents of the folder on disk. It’s important to
note, however, that the files that appear in a folder icon in the project navigator are not part of your project
unless you have added them to the project explicitly (in which case they appear directly under the project
or in a group, as well as in the folder). You can view and edit the files in a folder, but to move files in and
out of the folder you must use the Finder.
A file in the project navigator is a reference to a file on disk.


32

Get Oriented

Figure 1-15 shows a project (FolderFinder) containing both a group and a folder named ExtraFiles.
Although in the figure the group contains the same files as the folder, you could modify the contents of either
the group or the folder without affecting the contents of the other container.
Figure 1-15

A folder and groups in the project navigator

To add existing files to a project
1.

In the project navigator, select the project or group to which you want to add the files.
Note that you can’t add files to a folder in the project navigator. When you add a folder reference to
the project navigator, any changes you make to the contents of the folder in the Finder are shown
immediately in the project navigator.

2.

Choose File > Add Files to “ProjectName ”
.

3.

In the dialog, select the file or files you want to add and click Add.
If the file is not in your project folder on disk, you can choose to copy the file into your project folder.


33

Get Oriented

If you select a folder in the dialog and select the “Create folder references for any added folders” radio
button, Xcode adds a folder reference to the project navigator. Although the project navigator shows
the files that are in that folder on disk, Xcode does not add those files to your project. To add all the
files in a folder to your project, either select the files individually, or select the “Create groups for any
added folders” radio button.

Click the New Folder button to add a folder to the disk and a reference to that folder to the project
navigator. Doing so does not add any files to your project.
You can use the project navigator to organize the files in your project into groups and to list the files and
groups in any order you like. The jump bar shows the same project organization as the project navigator down
to the file that’s open in the editor, and then shows the individual symbols in the file.
Click the name of a file in the project navigator to see the file in the editor pane. The type of editor or viewer
that displays the file depends on the type of file you selected.

To create a new group
Do one of the following:


34

Get Oriented

●

●

Place the cursor at the location in the project navigator where you want the group, Control-click, and
choose New Group from the shortcut menu. You can drag files into the group, and you can drag the
group to a new location in the navigator.
Select the files that you want to place in a new group, Control-click, and choose New Group from
Selection. Note that you can Command-click items in the navigator to get a discontinuous selection.

Click the name of the group to edit the name.


35

Get Oriented

The project navigator has filters for recently edited files, files with source control status, unsaved files, and
filename strings. Figure 1-16, for example, shows a project filtered to show only implementation (.m) files. The
filter field and buttons are at the bottom of the navigator area.
Figure 1-16

The project navigator filtered to show only .m files

Once you’ve navigated to a file in the project navigator, you can see the path to that file displayed in the jump
bar (Figure 1-17). You can use the jump bar to navigate through your project.
Figure 1-17

Project navigation


36

Get Oriented

Use a jump bar to directly navigate to items at any level in your workspace.

To use the jump bar . . .
1.

Click a level in the jump bar and choose a file to jump to.

2.

To open a related file in Assistant, hold down Option and choose that file.

3.

In the Assistant jump bar, choose a category of related files.

4.

Use the stepper arrows to advance to the desired file.

5.

Click the lock button to open a locked file, if appropriate.

See the HTML version of this
document to view the video.

A jump bar is an interactive, hierarchical mechanism for browsing items in your workspace. Each editor
area includes a jump bar, as do Interface Builder and the documentation organizer. The configuration and
behavior of each jump bar is customized for the context in which it appears. The basic configuration includes
three components:
●

The related items menu ( ) offers additional selections relevant in the current context, such as recently
opened files or the interface (.h) file for an implementation (.m) file you are editing.

●

Previous/next buttons (

) allow you to step back and forth through your navigation history.

●

Thehierarchicalpathmenu(forexample,
)
comprises one or more segments. Click a segment to choose from the menu of the items at that level
of the hierarchy.
An example of a basic jump bar is in the documentation organizer. It simply allows you to select documents
from installed libraries. Other jump bars have more components.
A jump bar may also include a stepper for iterating through a set of files (
(

) or issues. If a lock button

) appears, you can click it and authenticate to unlock the file, if appropriate.


37

Get Oriented

Hold down the Option key when selecting an item in the navigation bar to open Assistant and display that
item in the Assistant editor pane. In the Assistant jump bar, the path menu is rooted relative to the content
of the regular editor pane, and the root element (flagged with a light-bulb icon) offers selections similar to
a related items menu.
The video shows using the jump bar to view the class SKTCircle and then using the Assistant jump bar
to view its superclasses.
Tip: Hold down the Command key when selecting a level in the path menu to view its items
alphabetically.

Note that every element in the path in the jump bar is a pop-up menu that you can use to navigate through
your project. Hold down the Option key when selecting a file in the jump bar to open Assistant and display
the file in the assistant editor pane (you can change this behavior in the General pane of Xcode preferences).
The contents of the jump bar depend on the type of file you’re viewing. In Interface Builder, for example, the
jump bar lets you navigate to individual interface elements (Figure 1-18).
Figure 1-18

The jump bar in Interface Builder


38

Get Oriented

The jump bar also has back and forward buttons for moving through previously viewed files, and a pop-up
menu (

) that displays a variety of useful information about related items, as shown in Figure 1-19.

Figure 1-19

The related items pop-up menu

Browse to Project Symbols
Click the Symbol button in the navigator selector bar to browse through the symbols in your project. Note
that you need to wait until Xcode finishes indexing your project before you can use this feature.

To browse the class hierarchy
●

Display symbols in a hierarchical or flat list using the buttons at the top of the symbol navigator.
Refine which symbols are displayed using the buttons at the bottom of the navigator. Buttons are blue
when toggled on and black when off. Use the buttons in any combination:
●

—hides symbols other than classes and their members, including protocols, functions, structs,
enums, unions, types, and globals

●

—hides symbols defined only in external frameworks, displaying only symbols defined in the
project or workspace,

●

—hides member symbols defined within the classes such as methods, properties, and variables

Further refine the results list by typing into the filter field at the bottom of the navigator.
Select a symbol to display its header file definition in the source editor.


39

Get Oriented

The screenshot shows one button toggled on and the word “drawing” in the filter field. In the resulting
list, the bezierPathForDrawing method is selected and its definition is highlighted in the source
editor.

●

Click an element in the jump bar to see a list of symbols at that level in the project hierarchy.

Tip: Hold down the Option key when selecting a file in the jump bar to open Assistant and display the
file in the assistant editor pane (you can change this behavior in the General pane of Xcode preferences).


40

Get Oriented

FInd Text Strings
Find text strings in your project or workspace with the search navigator.
Search a workspace or a find scope for text that matches specific criteria.

To search for text in projects and frameworks . . .
1.

In the search field, enter the search term.

2.

Specify the find criteria.

3.

Specify the find scope.

4.

Press Return.

5.

If desired, refine the results by entering a filter term in the filter field.

Use the find criteria to specify the style (textual or regular expression), attributes, and capitalization of the
text to find.
Use the find scope to confine your search to a particular location or set of files.
Use a filter term to remove any results that do not match it from the search list.
The screenshot shows the find criteria and find scope areas open, and search results for NSArray filtered
by the text circle.


41

Get Oriented

Tip: Option-click a search result to see it displayed in the assistant editor pane.

To customize the search, click the magnifying glass in the search field and choose Show Find Options to get
the Find Options dialog. You can specify the type of text and the scope of the search.
Figure 1-20 The Find Options dialog

You can also replace text you’ve found. See "Replace Text Strings" (page 215) for details.

View Issues Discovered by Xcode
The issue navigator lists messages, warnings, and errors that Xcode identifies in your code and your project,
including issues found by Fix-it, the static analyzer, and the compiler.


42

Get Oriented

When a build fails, the issue navigator opens automatically, displaying all the issues found in the code. Click
an issue to see it displayed in the source editor. You can also navigate through the issues using the arrows and
pop-up menu in the right end of the source editor jump bar. See "Locate and Display Build Issues" (page 183)
for more information on the issue navigator.
Figure 1-21

The issue navigator

Manage Breakpoints
Whereas you set breakpoints in the source editor, the breakpoint navigator (Figure 1-22) is where you can see
all your breakpoints in one place. In addition, you use the breakpoint navigator to add conditions and options
to breakpoints.


43

Get Oriented

For more information on using breakpoints in debugging your code, see "Manage Breakpoints" (page 188).
Figure 1-22 The breakpoint navigator


44

Get Oriented

View Threads and Stacks
When your running code hits a breakpoint (or you use the debug bar in the debug area to pause execution),
the debug navigator shows the current state of the stack in each running thread. Click an item in the navigator
to see it in your source code and to see the values of variables in the debug area (Figure 1-23).
Figure 1-23 The debug navigator and associated editor and debug areas

For more information on using the debug navigator while debugging your code, see "Examine Threads, Stacks,
Variables, and Memory" (page 200).


45

Get Oriented

View Build, Source Control, and Debug Session Logs
When you perform an operation that is normally recorded, such as building or analyzing your code, or that
has output to the console, such as a source control operation or a debug session, the record of that operation
is listed in the log navigator. Select an item in the navigator to see the log in the editor pane (Figure 1-24).
Figure 1-24 Viewing a log

You can use the filter button and text field at the bottom of the navigator to limit the logs displayed to recent
logs or logs whose names match the text string you enter.
The log viewer has two distinct displays:
●

For noninteractive tasks, such as building and source control, the log viewer displays a scope bar that you
can use to specify the content to display (see Figure 1-24).
Successful operations have a checkmark icon next to them. Operations with warnings have a warning icon
(an exclamation mark in a yellow triangle). Operations with errors have an error icon (an exclamation mark
in a red octagon) next to them. The right side of the operation indicates the number of warnings and
errors the operation produced.
To view an operation’s warning or error messages, click the disclosure triangle on the left side of the
operation.
To view an operation’s transcript, click the transcript button (

●

) on the right side of the operation.

For interactive tasks, such as debugging sessions, the log viewer displays a transcript of the session.


46

Get Oriented

Find Information that Supplements the Editor
There are several types of information located in the utility area of the workspace window, including Quick
Help, the File inspector, Interface Builder inspectors, and libraries of file templates, code snippets, Interface
Builder objects, and media files.
To open the utility area, choose View > Utilities, or click the Utility button in the toolbar (Figure 1-25).
Figure 1-25 The utility button


47

Get Oriented

View and Edit the Properties of Specific Items
Inspectors are panes in the upper portion of the utility area that you can use to read or enter data about files
and Interface Builder objects, among other things. Which inspectors are available depends on which editor
you’re using. Compare, for example, the inspectors available for data models (Figure 1-26) with those for
Interface Builder (Figure 1-27).
Figure 1-26 Data model inspectors

Figure 1-27 Interface Builder inspectors


48

Get Oriented

Get Templates, Files, and Interface Builder Objects
The libraries in the lower portion of the utility area (Figure 1-28) provide file templates and code snippets that
you can drag into your project or workspace, user interface elements that you can use in Interface Builder, and
the media files (graphics, sound files, and so forth) used in your workspace. For more details on the use of the
libraries, see "Incorporate Files and Code from the Xcode Libraries" (page 148).
Figure 1-28 The library pane


49

Get Oriented

Check on the Progress of Xcode Tasks
The activity viewer in the workspace window toolbar shows the progress of any task Xcode is currently executing.
If two or more tasks are currently underway, a small number appears at the left edge of the activity viewer
(Figure 1-29). Click the number to open a pop-up window that shows the individual status of each current task
(Figure 1-30).
Figure 1-29 The activity viewer

Figure 1-30 The activity pop-up window

If there were any issues the last time you built or analyzed your code, an icon in the activity viewer indicates
the number and severity of issues found (Figure 1-31). Click the issues icon to see the issues in the issue
navigator.
Figure 1-31

Issues in the activity viewer


50

Get Oriented
The Organizer Window: Managing Projects, Devices, and Documentation

The Organizer Window: Managing Projects, Devices, and
Documentation
Xcode has two main windows. You’ve seen the workspace window (Figure 1-2 (page 16)), used for editing,
debugging, and interface design. The other main window, called the Organizer window , displays documentation,
source control, project organization, and for iOS, access to your mobile devices. To display the Organizer
window, choose Window > Organizer, or click the Organizer button in the toolbar (Figure 1-32).
Figure 1-32 The Organizer button

Browse and Bookmark Documents
To browse documentation, open the Organizer window, click the Documentation button in the toolbar, and
click the Browse button at the top of the navigation pane (Figure 1-33).
Figure 1-33 The documentation navigator


51

Get Oriented

While reading any page of documentation, you can choose Editor > Add Bookmark or Control-click and choose
Add Bookmark for Current Page to bookmark that page. Click the Bookmark button in the navigator pane to
see a list of bookmarks (Figure 1-34).
Figure 1-34 The bookmarks navigator

To select which documentation sets to download, use the Downloads pane in Xcode preferences.

To set documentation preferences
●

Set preferences for updating developer documentation using the Documentation tab of the Downloads
preferences pane.
Documentation is installed in the form of documentation sets, often called doc sets . Apple doc sets for
key developer libraries are installed with Xcode, and access to updates for them is controlled by
subscription. For your convenience, Xcode can automatically keep these subscriptions up to date. This
feature is controlled by the option “Check for and install updates automatically,” which is selected by
default. If this option is selected, Xcode displays the date and time of the last check.


52

Get Oriented

To check for updates manually, click the Check and Install Now button. If no new updates are available,
Xcode displays a message to that effect. When an update for a doc set is available but not yet installed
on your system, Xcode displays an Install button on the subscription line for that doc set. Click that
Install button to download and install the updated doc set on your system.
To install non-Apple documentation, subscribe to the associated documentation feed. First, obtain the
web (RSS) feed URL from the publisher. Click the Add (+) button, as shown in the figure, follow the
onscreen instructions to enter the URL, and click Add in the dialog.
To remove a doc set from your system, select the subscription entry for the doc set, then click the doc
set info button. Click the Installed Location link to show the doc set file in the Finder, then delete the
file from the Finder.
To unsubscribe from non-Apple documentation, select the subscription entry for the doc set, click the
Remove (-) button and confirm the removal operation.
Note: You can remove an Apple doc set from your system, but you cannot remove the subscription to
its doc set feed.
At the bottom of the pane, you can set a minimum font size for documentation organizer content by
selecting the option "Never use font sizes smaller than," and then choosing a font size from the pop-up
menu.


53

Get Oriented

Browse for Task-Based Help
Online help is available for the Xcode IDE. To browse the Xcode online help, open the Xcode 4 Developer Tools
Library in the documentation navigator, then open Tools and Languages, then IDEs (Figure 1-33 (page 51));
or choose Help > Xcode Help to get the start screen shown in Figure 1-35.
Figure 1-35 Xcode help start screen

Many of the articles in Xcode help include a short video that illustrates the described procedure. Click the video
thumbnail to play the video.
To help you discover and understand the many user interface features of Xcode, most of the help articles are
also available as contextual help. See "Contextual Help: Your Shortcut to Answers" (page 15) for details.

Work with Your Source Control Repositories
Click the Repositories button in the Organizer window toolbar to work with your source control repositories.
You can create local repositories, connect to and manage repositories on servers, and so forth. You can also
perform many common SCM operations, such as submitting files, from the workspace window. To do so, select
the file or files in the project navigator, Control-click, and choose Source Control from the menu. See "Keep
Track of Changes with Source Control " (page 253) for details.


54

Get Oriented

Organize Your Projects and Devices
Whereas Xcode allows you to have several workspace windows open simultaneously, there is only one Organizer
window. The Organizer window displays information for all your workspaces, projects, repositories, devices,
and documentation, regardless of how many projects you have and how many are open.
Click the Projects button in the toolbar to display all your projects, their snapshots, and archives.
If you’re working with iOS, the Xcode Organizer window also can display the devices that you have connected
to your computer. It indicates which of these devices are currently available and lets you select the one to use.
For more information on the use of iOS devices with Xcode, see "Manage Your Devices" (page 225).

Take a Snapshot of Your Project
To save a snapshot of your project, choose File > Create Snapshot. Note that you must have selected System
Tools in the Xcode installer in order to use snapshots. System Tools are selected by default.
To see what snapshots have been saved in Xcode, open the projects organizer and click the project in which
you’re interested. For more information on snapshots, see "Take a Snapshot of Your Project" (page 252).


55

Start a Project

This chapter tells you how to start a new Xcode 4 project, either by creating a new project from scratch, or by
opening an existing Xcode 3 project. Once you’ve got your projects open, go to "Get Oriented" (page 15) to
learn more about using Xcode 4.

Click New Project in the Xcode 4 Startup Screen to Create a
Standalone Project
If you want to start a new software development undertaking using Xcode 4, you need to first decide whether
you need a single Xcode project or multiple related projects. For a simple application or utility, a single project
should suffice. However, if you have several related executables that need to link against a custom library, you
probably want at least a separate project for the library and another for the executables, and possibly a separate
project for each executable.
Start developing a software product by creating a project. All software products require a project. The project
organizes the files and resources needed to build one or more products, such as applications, plug-ins, and
command-line tools.

To create a standalone project . . .
1.

Choose File > New > New Project.

2.

Select the project template for your iOS or OS X product, and click Next.

3.

Enter the product name and other project details, and click Next.

4.

Specify the project’s location in your file system, and click Save.



56

Start a Project
Click New Project in the Xcode 4 Startup Screen to Create a Standalone Project

The New Project dialog displays platforms, template families, project templates, and a description for the
selected project template. In the project options pane you enter information required by the template to
generate the project, such as the product name.
Note: The New Project dialog appears in the workspace window for the workspace to which
Xcode will add the project. When you create a project with no workspace window active, the
New Project dialog is attached to a new workspace window that contains only the new project.

The project location in your file system and its container in the workspace window are both derived from
your selection in the project navigator when you initiated the New Project command. That is, if you have
a project selected in the project navigator, Xcode places the new project inside the selected project. The
Save dialog lets you specify a different location and container for the new project before completing the
operation. For example, you can indicate that the container of the project be a group within your workspace
instead of the workspace itself.
The video shows how to create a project named MyProject and place the project directory on the Desktop.
After saving the project, Xcode places a folder containing the new project’s files at the location you specified.
Once you’ve created a project, you can add new source files and begin writing code.
If you have two or more closely related projects, you should create a workspace and add your projects to it, as
described in "Create a Workspace to Work with Multiple Related Projects" (page 59).


57

Start a Project
Click New Project in the Xcode 4 Startup Screen to Create a Standalone Project

Create a Git Repository For Your New Project
You can create a local Git repository when you save the new project (Figure 2-1). This is the easiest way to add
source control to a project (see "Keep Track of Changes with Source Control " (page 253) for more information).
Figure 2-1

The option to add source control when creating a project

Select Options While Creating a New Project
Both Mac OS X and iOS support use of the Core Data frameworks. To add core data modeling to your new
project, select the Use Core Data option in the New Project dialog. See "Design Data Models Graphically" (page
26) for more information.


58

Start a Project
Create a Workspace to Work with Multiple Related Projects

You can also choose to use automatic reference counting, include unit tests, or include Spotlight Importer in
your project (Figure 2-2). The files that Xcode creates for your new project depend on the options you select
in the new project dialogs.
Figure 2-2

Options for a new project

Note that Core Data is an advanced technology that is not required for creating simple applications.
To add automatic reference counting (ARC) to an existing project, see "Add Automatic Reference Counting" (page
64).

A major feature of Xcode 4 is the ability to create a container for multiple projects that you can use to group
Xcode projects and other files that are related. This container is referred to as an Xcode workspace . All the
projects in the workspace share the same build directory. Putting your related projects in the same workspace
affords you several benefits, including:
●

●

●

One project can use the products of another project while building.
If one project depends on the products of another in the same workspace, Xcode can detect this and
automatically build the projects in the correct sequence.
Because all the files in one project are visible to all the other projects in the workspace, you don’t need to
copy shared libraries into each project folder separately.


59

Start a Project

●

Indexing is done across the entire workspace, extending the scope of content-aware features such as code
completion.

To create a workspace
1.

If Xcode is not open, open it. You can ignore or cancel the startup screen. If you already have an Xcode
project open, go on to the next step.

2.

Choose File > New > New Workspace.

3.

In the New Workspace dialog, specify the location for the workspace file and the name of the workspace.
If your projects are in the same directory, it might be convenient to put the workspace file in there as
well. Click Save.
Tip: To avoid possible confusion with your projects, give the workspace a unique name.

You now have a workspace with no projects in it. You can add existing projects to the workspace, or create
new ones.
You can add any existing project to the workspace, or Control-click in the structure navigator below the existing
projects and select New Project to create a project in the workspace.


60

Start a Project

Add an existing project to a workspace to add a product to a multiproduct development endeavor. When you
need to work on two or more related projects, you can add them to a workspace so that you can create
interproject relationships.

To add an existing project to a workspace . . .
1.

In the project navigator, Control-click in the empty space below the list.

2.

Choose Add Files to “<WorkspaceName>”
.

3.

Navigate into the folder containing the project package.

4.

Select the project package and click Add.


For example, you can have a workspace with an application project, add a framework project to the
workspace, and make the application dependent on the framework. When you build the application, Xcode
builds the library first, if it needs to be built.
When adding a project to a workspace, you add the project package. A project package is a directory that
the Finder displays as a file. It contains information about the project, such as references to the files that
are part of the project, the project’s groups, build settings, and target definitions.
The video shows the process of adding a second project, called MyFramework, to a workspace called
MyWorkspace.
After you add a project to your workspace, the project appears in the project navigator.


61

Start a Project

Alternative: You can drag a project package from a Finder window or a workspace window to
the project navigator in a workspace window to add the project to the second workspace. When
doing so, ensure that you add the project package to the root of the project navigator and not
a project within it.

Note: If you choose File > New > New Project while any project is selected, or Control-click inside
an existing project and choose New Project, Xcode adds the project file inside the currently selected
project. The only way to undo this operation is to delete the new project. Figure 2-3 shows the
shortcut menu you get when you Control-click below the existing projects. Note that, in this case,
the Add Files menu item specifies the name of the workspace, not of one of the existing projects.
Figure 2-3

A shortcut menu for a workspace

Because each project retains its individual identity, a project can be included in more than one workspace or
removed from a workspace without affecting the project. The workspace file itself merely contains pointers to
the projects and other files that the workspace includes, plus a minimal amount of data such as schemes stored
in the workspace. The pointers to the source files, included libraries, build configurations, and other data are
stored in the project files.


62

Start a Project
Check Out a Working Copy from Your Source Control Repository

Tip: If you have an Xcode project and would like to create a workspace to contain it, choose File > Save as
Workspace. You can assign a new name to the workspace and specify a location for the workspace file. Doing so
does not alter the original project or prevent you from adding the project to another workspace as well.

If the build product of one project in a workspace is dependent on the build product of another project in the
workspace (for example, if one project builds a library used by the other project), Xcode discovers such implicit
dependencies and builds in the correct sequence. If you don’t want one project to use the product or files in
another project that’s in the same workspace, you need to adjust your build settings accordingly. See "To add
a new build configuration" (page 66) for help in finding and understanding the build settings interface in
Xcode.
Before you build, be sure you’ve created the scheme or schemes you need. See "Create, Edit, and Manage
Schemes" (page ?) for more information on schemes.

Check Out a Working Copy from Your Source Control Repository
If your Xcode project is in a Git or Subversion repository, you can check out your project from the repository
and open it in Xcode. See "Keep Track of Changes with Source Control " (page 253) for more information on
using source control in Xcode.

Modernize Your Project
When you open a project, Xcode 4 evaluates it to see whether there are any settings that should be updated.
This feature provides an easy way to make sure your projects conform to the latest SDKs and best practices.
Open the issue navigator (Figure 2-4) to see whether anything in your project needs to be updated. You can
also select the project in the project navigator and choose Editor > Check for Outdated Settings, or choose
the project from the the drop-down issues menu at the right end of the jump bar.
Figure 2-4

Modernization in the Issue navigator


63

Start a Project
Add Automatic Reference Counting

If the issue navigator lists modernization issues, click the issue to see a dialog that explains the updates that
should be made (Figure 2-5). Deselect any checkboxes for settings you don’t want to change, then click Perform
Changes to update the project to optimize it for Xcode 4.
Figure 2-5

Updates dialog

After you have clicked Perform Changes, whether you choose to make all the changes or not, Xcode does not
show the warning again. To rerun the check, select your project in the project navigator and choose Check for
Outdated Settings from the Editor menu.

Add Automatic Reference Counting
Xcode 4.2 and later includes a menu item to convert existing targets to use Automatic Reference Counting
(ARC), which automates memory management for Objective-C objects. ARC makes memory management
much easier, greatly reducing the chance that your program will have memory leaks. First, Xcode reviews your
project to determine whether there are items that cannot be converted (and that you must therefore change
manually). Then, Xcode rewrites your source code to use ARC. (To add ARC to a new project, see "Select Options
While Creating a New Project" (page 58).)
To initiate the process, enable Continue building after errors in the General Preferences pane, then choose
Edit > Refactor > Convert to Objective-C ARC. The targets that you convert are updated to build using the
Apple LLVM compiler. Xcode attempts to build your target and to determine what changes must be made to


64

Start a Project
Close a Project or a Workspace

use ARC. If it finds any issues that prevent conversion, Xcode displays a dialog directing you to review the
errors in the Issue navigator. After you correct the errors, choose the Convert to Objective-C Automatic Reference
Counting menu item again to restart the ARC-conversion workflow.
When Xcode successfully builds your application, it takes a snapshot of the current code so that you can revert
later if you want to. Then Xcode displays a preview dialog showing the changes it’s going to make. When you
accept the changes, Xcode converts your code to use ARC.
For more information on ARC, see Transitioning to ARC Release Notes .

Close a Project or a Workspace
Choose Close Project or Close Workspace from the File menu to close a project or workspace without closing
Xcode. In Xcode 4.1 and later, Xcode remembers which windows you had open and how they were configured,
and restores them when you reopen the project or workspace. Also in Xcode 4.1 or later, pressing
Command-Option-W or holding down the Option key and clicking the close box closes the project or workspace
without first closing all windows and tabs. In this way, your window configuration is restored the next time
you open the project.


65

Configure Your Project

During the course of developing an application, you need to build, run, and debug your code. As part of
optimizing your code and ensuring quality control, you might also run unit tests, perform static analysis, and
use profiling tools to find memory leaks, inefficient routines, and other run-time problems. Finally, you’ll
probably want to archive your application in order to share it with others or submit it for inclusion in the App
store.
In order to carry out all these actions, you need to edit a few basic build settings and set up one or more
schemes to specify the targets, build configuration, and executable configuration to use for each type of action.
In Xcode you use the project editor and the scheme editing dialog to customize your builds and control what
happens when you build and run your code.

Add Build Configurations
When you create a project, Xcode provides two build configurations: Debug and Release, which differ primarily
in the inclusion of debug information and in the degree to which the build is optimized. You might want to
add more build configurations; for example, you might want a build that’s fully optimized but that includes
debug information in order to debug the optimized code.

To add a new build configuration
1.

Select the project in the project navigator to open the project editor.

2.

Select the project in the project editor and click the Info button.

3.

Expand the Configurations section in the Info pane and click the Add (+) button at the bottom of the
section.


66


4.

Select one of the existing configurations from the pop-up menu as a starting point for the new
configuration.

5.

Select the name of the copy and type your preferred name for the configuration.


67


6.

Click the Build Settings button to display the build settings for the project.

7.

To change the build settings in the new configuration for all the targets in the project, edit them at
the project level. To change the build settings for an individual target, select that target.

8.

Select each build setting you want to edit and click the disclosure triangle to display the list of build
configurations.

9.

Select the new configuration and edit the setting.

You can use a build configuration file to set and to share build configurations. A build configuration file is a
plain text file with the filename extension .xcconfig that contains a list of build setting definitions, one per
line. The build configuration file must be in your project.
Configure a uniform set of build setting definitions across any number of targets or projects by using a
configuration file. A configuration file is a plain text file with a list of build setting definitions, one per line. You
can base a build configuration only on a configuration file that is in your project, not on an external file.

To base a build configuration on a configuration file . . .
1.

In the project editor, select the project for which you want to use a build configuration file.

2.

Click Info at the top of the project editor.

3.

In the Configurations section, navigate to the build configuration you want to base on a configuration
file.


68

Set the Basic Build Settings

4.

Choose a configuration file from the pop-up menu in the right column.


When you base a target or project’s build configuration on a configuration file, that build configuration
automatically inherits the build setting definitions in that configuration file (and any configuration files it
includes). If you then modify the value of any of those build settings in the target or project, the new value
is used instead of the value in the configuration file.
Build settings defined at the target level override any values assigned to those build settings at the project
level. Therefore, target-level configurations take precedence over any project-level configurations.
The video shows basing the Debug build configuration on a file called Config.xcconfig at the project
level.

When you create a new project, it includes one or more targets, where each target specifies one build product
and the instructions for how the product is to be built. You can use the project editor to specify every aspect
of the build, from the version of the SDK to specific compiler options.
Most developers never need to change the default of the vast majority of the build settings. However, there
are a few basic settings that you must check, and possibly edit, for each target. These settings are gathered
into one pane in the project editor—labeled the Summary pane—and are somewhat different for Mac OS X
and iOS projects.

To edit the basic build settings for Mac OS X targets
1.

In the project editor, click the target.


69


2.

At the top of the project editor pane, click the Summary button.

3.

To select an icon for your product, Control-click the App Icon image well and choose Select File (or
drag an icon file directly to the image well).

4.

To add a linked framework or library to your target, click the Add (+) button at the bottom of the Linked
Frameworks and Libraries section.
For example, to provide your target with access to audio hardware, add the Core Audio framework.

Each setting in the Summary pane is also found in one of the other panes. When you edit a setting, Xcode
updates the other pane automatically. Table 3-1 lists each setting in the Mac OS X Summary pane along with
the corresponding target setting and location.
Table 3-1

Mac OS X project editor Summary pane settings

Summary pane setting

Target setting

Pane

Identifier

Bundle identifier

Info

Version

Bundle version

Info


70



Target setting

Pane

This app runs on Mac OS X

Mac OS X Deployment Target

Build Settings

Main interface

Main nib file base name

Info

App icon

Icon file

Info

Linked frameworks and libraries

Link Binary With Libraries

Build Phases

To edit the basic build settings for iOS targets
1.

In the project editor, click the target.

2.

At the top of the project editor pane, click the Summary button.

3.

Select an icon for your app.


71

Add Build Rules

Control-click one of the App Icons image wells and choose Select File (or drag an icon image into the
image well).
4.

Select a launch image.
Control-click one of the Launch Images image wells and choose Select File (or drag an image into the
image well). You can drag a launch image directly from the Screenshots library in the Devices pane of
the Organizer window.

5.

Choose a target device from the Devices pop-up menu.
Choose Universal to configure your iOS app to run on both iPhone and iPad.

As for Mac OS X projects, each setting in the Summary pane for an iOS project is also found in one of the other
panes. When you edit a setting, Xcode updates the other pane automatically. Table 3-2 lists each setting in
the iOS Summary pane along with the corresponding target setting and location.
Table 3-2

iOS project editor Summary pane settings


Target setting

Pane

Identifier

Bundle identifier

Info

Version

Bundle version

Info

Devices

Targeted Device Family

Build Settings

This app runs on iOS

iOS Deployment Target

Build Settings

Main Interface

Main nib file base name

Info

Supported Device Orientations

Supported interface orientations

Info

App Icons

Icon files

Info

Launch Images

Launch Image

Info

Add Build Rules
Xcode processes your source files according to the file type using a set of built-in rules. For example, property
list (plist) files are copied into the product using the CopyPlistFile script located in the Xcode directory.


72

Add Build Rules

To see the default build rules for a target
1.

Select the project in the project navigator.

2.

In the project editor, select the target and click the Build Rules button.
Because Xcode sets build rules on a per-target basis, no build rules are displayed when you select the
project rather than a target.

3.

At the top left of the Build Rules pane, click the All button.

To customize a build rule for a target
1.

Display the default build rules for the target ("Add Build Rules" (page 72)).

2.

At the right margin of the build rule you wish to customize, click the Copy to Target button.

3.

Fill in the build rule template that appears.


73

Add Build Rules

4.

Click the Target button at the top of the Build Rules pane to see and edit the customized build rules
you’ve added.

You can click the Add Build Rule button at the bottom of the Build Rules pane to create a new build rule.
Change the way files are processed with build rules.

To add a build rule . . .
1.

In the project editor, select the target to which you want to add a build rule.

2.

Click Build Rules at the top of the project editor.

3.

Select Target at the top of the Build Rules pane.

4.

Click Add Build Rule in the lower-right corner.

5.

Choose a file type from the Process pop-up menu.


74

Add Build Rules

6.

Choose a compiler from the Using pop-up menu.

You can define build rules on a per-target basis. Target-specific build rules can specify files that the system
build rules do not directly address and can override the existing system build rules, which are predefined
and unmodifiable.
The Process and Using menus include many types of files and many compilers, but you can specify custom
file types or compilers by choosing “Source files with names matching:” from the Process menu or “Custom
script:” from the Using menu.
The screenshot shows a build rule that compiles C source files with GCC 4.2 rather than the default compiler.


75

Edit User Interfaces

You design user interfaces in Xcode using Interface Builder. Interface Builder is an Xcode editor that provides
a graphical interface for the creation of user interface files. Like other Xcode editors, Interface Builder is fully
integrated into the application, so you can write and edit source code and tie it directly to your user interface
without leaving the Xcode workspace window.
When you create a new Mac OS X or iOS application, Xcode includes one or more Interface Builder files in the
project. These files, called nib files, may have the filename extension nib or xib. Similarly, when you create a
new view controller, Xcode includes a nib file along with the header and implementation files for the new
class. For iOS applications, you can use storyboards instead of nib files, as described in "Design the User Interface
of Your iOS App with Storyboards" (page 92).

Create Your User Interface
Interface Builder, like other Xcode editors, has associated inspectors and libraries in the utility area. Interface
Builder appears in the editor area of the workspace window when you select a nib file or storyboard file in the
project navigator. When you open a nib or storyboard file, your user interface objects appear in the editor area
and the Interface Builder inspectors appear in the utility area. You use these inspectors to configure the interface
objects and to make connections between them. The Object and Media libraries in the library pane of the
utility area are also for use with Interface Builder—you use these libraries to add new objects to your user
interface design.


76


Figure 4-1 shows Interface Builder and associated panes open in the workspace window. You can select Interface
Builder objects and media files in the library pane and drag them onto the Interface Builder canvas. You can
also open an assistant editor, which shows a file or files associated with whatever object you’ve selected in the
Interface Builder pane.
Figure 4-1

Interface Builder in the workspace window


77


Display Your User Interface Objects
The dock on the left side of the Interface Builder pane shows the Interface Builder objects and placeholders in
your nib or storyboard file. The dock can display the high-level objects in an icon view (Figure 4-2) or in a list
(called the outline view ) showing all the objects nested in higher-level objects. Storyboard files show only the
outline view in the dock; however, each scene in the storyboard has its own scene dock displayed below it
when you select the scene (see, for example, Figure 4-11 (page 95)).
Figure 4-2

Icon view for placeholders and objects in Interface Builder

Add new objects to an Interface Builder document using the outline view, a hierarchical tree that reflects the
parent-child relationships between the objects in the nib file.

To add an object using the outline view . . .
1.

With a nib file open, toggle the dock to outline view, if necessary, by clicking the dock mode button
at the bottom of the dock.

2.

Navigate to the place in the outline where you want to add the object.


78


3.

Drag an object from the Object library (in the utility area) into the outline.


The video shows how to add a text formatter object to a text field cell using the outline view.

Tip: To return to the icon view, click the dock mode button (

) again.

Note that you can also use the Interface Builder jump bar to select any object in the interface.

Connect to Other Files Using Placeholder Objects
There are two kinds of objects displayed in the Interface Builder dock: Interface objects and placeholder objects.
Interface objects are the objects that are actually created when the nib file is loaded and typically comprise
the bulk of the objects. Placeholder objects refer to files that live outside of the nib file but which are intimately
tied to the contents of the nib file. There are normally three placeholder objects in a nib file:
●

File’s Owner

●

First responder

●

Application

File’s Owner
File’s Owner Represents the nib file’s controller object. File’s Owner is the most commonly used placeholder
object in nib files and is supported by both Mac OS X and iOS nib files. The File’s Owner placeholder is the
main bridge between your application and the contents of the nib file.
When you build and run your application, the nib-loading code substitutes the object that is the file’s owner
for any references to the File’s Owner placeholder in the nib file. This substitution results in the outlets and
actions connected to the File’s Owner placeholder being connected to the object that is the file’s owner.
You can designate any object in your application as the File’s Owner of a nib file. You tell Interface Builder the
class of the File’s Owner so it knows what connections to make available. Typically, the file’s owner is a controller
class that manages the interactions with the views and other controller objects inside the nib file.


79


To configure the File’s Owner placeholder
1.

Select the File’s Owner placeholder object in the Interface Builder dock

2.

Open the Identity inspector.

3.

In the Class field of the Custom Class section, set the class of the File’s Owner to the corresponding
class in your application.
The following table lists some of the standard classes that are commonly used to represent File’s Owner
in applications:
Subclass of

Description

NSDocument

Mac OS X

Document-based applications store the document
window and other required interface objects in a
nib file. The File’s Owner of this nib file is
traditionally the document object itself.

NSWindowController

Mac OS X

Window controllers provide a great deal of
automatic management for nib files and are
especially useful when your nib file contains only
one window.

NSViewController

Mac OS X

A view controller manages custom accessory views
and other view-based content.

UIViewController

iOS

A custom UIViewController object is often used
to manage the content view for a distinct screen’s
worth of content. A UI view controller provides
automatic nib-loading and purging support.

Any custom NSObject
subclass

4.

Operating
System

Mac OS X
or iOS

You can use practically any object you like for
manual control of a nib file. It is up to you to define
the relationships between this class and the objects
in your nib file.

Control-click the File’s Owner object to see the outlets and actions defined by that class.

To learn about outlets and actions, see "Manage Connections Between User Interface Objects" (page 106).
You can use these outlets and actions to connect other objects to File’s Owner. You can use File’s Owner
as a target for your bindings. For information about connecting to File’s Owner, see "Make Connections
Directly Between IB Objects and Your Code Files" (page 107).


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First Responder
The First Responder placeholder object represents the first object in the responder chain, which is determined
dynamically at runtime by the AppKit and UIKit frameworks.

To add new action messages to the first responder’s supported list
1.

Select the First Responder placeholder object in your Interface Builder document.

2.

Open the Attributes inspector.

3.

Click the Add (+) button at the bottom of the User Defined section to create a new action method
entry.

4.

Double-click the method name in the Action column and type the name of the method.

5.

Select the class in which the method will be defined from the pop-up list in the Type column.

6.

After you are done making connections in Interface Builder, add the code for the method to the header
and implementation class files in your project that you specified in step 5.
The name of the method must match the name specified in step 4.

Adding action methods to the First Responder placeholder object does not add the corresponding method
definition to your Xcode source files. All it does is let Xcode know that such a method exists in one of the
objects in the responder chain of your project. It is up to you to ensure the method names you add to the
First Responder placeholder match the names of the methods in your code. Xcode does not validate these
method names for you. At runtime, if a method name is misspelled or does not exist in an object, the
corresponding action message is never received by the target object.
Interface Builder does not prevent you from deleting the standard system messages associated with the
First Responder placeholder. Doing so removes the message name from the current nib file only.
When Mac OS X or iOS sends a message to your application, the message is sent to your application’s first
responder. The first responder is typically the currently selected object or the object with the current focus in
the frontmost window. You use the First Responder object to make connections to any messages that operate
on the current selection or need to be handled by your frontmost window or document. For example, if you
wanted a menu command to be handled by your frontmost window, you would dispatch that command to
your First Responder object.
The First Responder placeholder displays all of the actions that are either supported natively by the operating
system or defined in your Xcode source files.


81


Note: The First Responder placeholder is only for configuring action messages. You cannot connect
the First Responder placeholder object to one of your custom outlets in hopes of receiving a
dynamically changing pointer to the selected object in your window. In Mac OS X applications, you
should instead use the firstResponder method of the current NSWindow object to get the first
responder. In iOS applications, there is no single first responder object; the first responder is always
the view that is the target of a touch.

Application
In Mac OS X nib files, the Application placeholder object gives you a way to connect the outlets of your
application’s shared NSApplication object to custom objects in your nib file. The default application object
has outlets for its delegate object and, in Mac OS X applications, the application menu bar. If you define a
custom subclass of NSApplication, you can connect to any additional outlets and actions defined in your
subclass.
At load time, the nib-loading code automatically replaces the Application placeholder object with the shared
application object from your application.

Select Hidden Objects in an Interface File
In Xcode, you can usually select an object in a nib or storyboard file by clicking it directly from the Interface
Builder canvas. Many objects are compound, however, such as a text field that contains a number formatter.

To select a hidden UI object using the dock
1.

Expand the dock to show the outline view.

2.

Use the disclosure triangles to open the objects containing the object you want to select.


82


3.

Select the object in the outline view.

Tip: You can make connections directly between the object in the dock and source code or other objects.

To select a hidden UI object using the jump bar
1.

If the top-level window or UI object is not already displayed on the Interface Builder campus, select
the window or object in the dock.

2.

With the UI design displayed on the Interface Builder canvas, select an object in the jump bar that
contains the object you want to select.
Tip: You can select the top-level object or any object in the hierarchy that contains the target
object. You cannot navigate to a hidden UI object in the jump bar by selecting the nib file itself.


83

Lay Out User Interface Controls Using Content-Driven Rules

3.

Navigate through the chain of pop-up menus to the object you want to select.

Interface Builder supports the AppKit Auto Layout feature. Auto Layout, available starting with Mac OS X v10.7
Lion, uses relationships called constraints to govern the layout of objects in the user interface. This feature is
a complete replacement for the autoresizing mask. As you make changes to any view or control in Interface
Builder (move it around, resize it, change an attribute, add a subview, and so forth), Interface Builder
automatically adds and removes constraints based on the new layout. When you enable this feature, Interface
Builder shows the constraints as you work, as shown in Figure 4-3.


84


Note: Auto Layout is available only in Mac OS X v10.7 Lion and later. If you are running Xcode 4 in
Mac OS X v10.6 Snow Leopard, Auto Layout is not available.
Figure 4-3

Auto Layout

You must enable Auto Layout per nib.

To enable Auto Layout
●

Select the Use Auto Layout checkbox in the File inspector for each nib.
If you are converting many nib files, you can select all of the nib files at the same time (use the Project
Navigator to filter for xib or nib) and enable Auto Layout for all of them at once.

When you enable Auto Layout, Xcode updates your build settings, if necessary, to ensure your deployment
target is Mac OS X v10.7 or greater. For nib files in projects that had been targeted for Mac OS X v10.6 or
earlier, Interface Builder adds constraints to your nib files automatically when you enable Auto Layout.
Interface Builder treats constraints like other objects in a nib file. Like other objects, the constraints for a view
are visible in three places:

To see the constraints in a view


85


●

In the jump bar, select the object that contains the constraint.

●

Select a object on the canvas.

●

Open the IB dock to the outline view.
All the constraints are grouped, listed, and selectable in the outline view of the dock.


86


Add New Constraints
Constraints are selectable. When you select a constraint, you can use the Attributes inspector to change its
attributes and you can make connections from or to it. You can also select multiple constraints.
You specify constraints in terms of leading or trailing edges and top or bottom rather than left and right or
X,Y values. Leading and trailing edges can be localized for languages that read right-to-left, and specifying top
or bottom avoids the possible confusion caused by coordinates that are y-down (minimum y value on top)
versus y-up (minimum y value on bottom).
Apple encourages you to use standard aqua spaces for your spacings. Interface Builder snaps to these spacings
when you are dragging or resizing views in the canvas.

To set standard spacing for a constraint
1.

Select the constraint.

2.

In the Attributes inspector, select the Standard checkbox.

You can edit an automatic constraint or add your own.

To add a constraint
1.

Select the object or objects for which you want to add the constraint.

2.

Choose a constraint from the Editor > Add Constraint menu or an alignment type from the Editor >
Alignment menu.


87


Any constraint that you have modified or added manually is considered a user constraint and is shown on the
canvas with a thicker line than used for the automatic constraints. In the figure, the user constraint is the one
affecting the width, and the connections to the superview are automatic constraints.
Figure 4-4

User constraint

Table 4-1 lists the types of Auto Layout constraints.
Table 4-1

Auto Layout constraints

Constraint

Figure

Notes

Size (width or
height)

Select the object and choose
Editor > Add Constraint >
Width or Editor > Constraint
> Height. Use the Attributes
inspector to specify the value
of the constraint. For example,
“equal to 80 pixels,” or “less
than or equal to 150 pixels.”
The figure shows a constraint
that keeps the width of a
button greater than or equal
to some number.


88


Constraint

Figure

Notes

Equal size

Select all the objects that you
want to include and then
choose either Equal Widths or
Equal Heights from the Editor
> Add Constraint menu. If all
the objects involved maintain
their intrinsic content size (see
"Allow Objects to Maintain
Their Intrinsic Content
Size" (page 90)), then the
width or height of the objects
is that of the largest object in
the group. If one of the
objects has an explicit size,
then the other objects assume
the same explicit size.

Spacing

Select two objects and then
choose either Horizontal
Spacing or Vertical Spacing
from the Editor > Add
Constraint menu. The figure
shows a button and a text
field with a set distance
between them.

Superview-spacing

Select an object an choose
one of the superview
commands from the Editor >
Add Constraint menu: Leading
Space to Superview, Trailing
Space to Superview, Top
Space to Superview, or
Bottom Space to Superview.
Use the Attributes inspector
to specify the space between
the object and its container.
The figure shows a constraint
holding the leading edge of a
button the standard aqua
space from the leading edge
of the container.


89


Constraint

Figure

Notes

Alignment

Select all the objects that you
want to include and then
choose an item from the
Editor > Alignment menu.
Alignment constraints are
drawn as a straight line rather
than an I beam. For example,
in the figure, the label and
text field are aligned along
their baselines.

You can edit constraints to specify such features as absolute or relative widths or heights.

To edit a constraint
1.

Select the constraint.

2.

In the Attributes inspector, specify the type and value of the constraint, along with any other options.

Allow Objects to Maintain Their Intrinsic Content Size
If there are no explicit constraints for width or height, an object assumes its intrinsic content size , which is the
minimum size the object needs to be to hold its contents. For buttons, that might be the title, an image, or
both. For text fields, the contents consist of the string and the bezel, for a combo box, the string in the text
field and the disclosure button, and so forth.
Some objects have an intrinsic content height, but not width. Others, such as buttons, have both an intrinsic
height and width. Some objects, such as table views, have no intrinsic content size. When an object is set to
maintain its intrinsic content size, it resizes as needed to accommodate changes, such as differences in the
length of text strings due to localization.
As opposed to an object with an explicit size, an object that maintains its intrinsic content size (and has no
other size restraints) does not have the I-beam size constraint under it, as shown in Figure 4-5. To specify
intrinsic content size, select the object and choose Size to Fit from the Editor menu.
Figure 4-5

Button set to maintain its intrinsic content size


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Override Automatic Constraints
You can delete a user constraint, but not an automatic constraint. Rather than trying to delete automatic
constraints, create the constraints you want. For example, suppose you place a button in the content view of
a window and Interface Builder pins it to the upper leading edge of the window (Figure 4-6).
Figure 4-6

Automatic constraints

To pin the button to the trailing edge instead, add a constraint from the trailing edge of the button to the
trailing edge of the window (Figure 4-7). Interface Builder then automatically deletes the leading constraint
because the constraint you specified takes precedence.
Figure 4-7

User-added trailing constraint


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Design the User Interface of Your iOS App with Storyboards

If you want to pin the button to both sides, you can then add a second user constraint (Figure 4-8).
Figure 4-8

User-added leading constraint

Set Priorities to Resolve Potential Conflicts
Occasionally, two constraints can come into conflict when a view is being resized. For example, you might
have set your buttons not to get below a certain size, and also set a minimum width for the view containing
the buttons. You can determine whether the minimum size for the window in this case is determined by the
view width constraint or the button width constraint by specifying a lower priority for one than the other. For
example, if you set the priority for the button width constraint to 50 while the priority for the view width
constraint is 1000, Auto Layout will allow the view to be reduced to its minimum width even if it means reducing
the size of the buttons.

In Xcode 4.2, the Interface Builder user interface for iOS applications is based on the storyboarding of view
controllers. Storyboarding enables you to use Interface Builder to specify not only all the screens in your
application, but the transitions between them and the controls used to trigger the transitions. Thus you can
lay out every possible path through your application graphically, greatly reducing the amount of code you
need to write for a complex multiscreen application.


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To create a project that uses view controllers, choose File > New > New Project and select the Use Storyboard
checkbox in the options dialog (Figure 4-9).
Figure 4-9

The Use Storyboard option


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You start with a view controller object that represents your first scene (the initial view controller ). To get view
controllers for your storyboard, select Objects and Controllers from the Object library (Figure 4-10) and drag
the view controllers you want onto the canvas. Each view controller manages a single scene. On the iPhone,
each scene represents the contents of a single screen. For iPad applications, a screen can be composed of the
contents of more than one scene.
Figure 4-10

View controllers in the object library

To storyboard your application, you link each object that’s in a view controller and that can cause a change in
the display, to another view controller that configures and implements the new scene (Figure 4-11). You link
the various view controllers in Interface Builder by Control-dragging between controls and view controllers.


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You can drag from any control that has an output to the header of any other view controller. You can add
controls and views to each view controller’s view just as you would add objects to a window or a view in the
nib file of an Xcode 3 or Xcode 4.0 application.
Figure 4-11

Creating a storyboard

The arrows between view controllers represent the segues from one scene to another. To configure a segue—for
example, to specify the kind of transition to use between scenes—click the arrow and open the Attributes
inspector (Figure 4-12). To define a custom transition, select Custom for the style of the segue and fill in the


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name of your custom segue class. Standard segue classes are in UIKit (see UIKit Framework Reference ). For
information about implementing the methods in the UIViewController class, see UIViewController Class
Reference .
Figure 4-12

Attributes inspector for a segue


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Create User Interface Classes

The result is a storyboard that graphically represents every screen of your application and the flow of control
among the screens. Double-click the canvas to zoom out to see the entire storyboard (Figure 4-13).
Figure 4-13

Storyboard for an iOS Application

If you need a custom view object or a view controller, you create the new classes in the project navigator. Once
you’ve created the interface and implementation files, you can connect user interface objects in an Interface
Builder nib file or storyboard directly to your code files or you can add connections in the nib file or storyboard
between Interface Builder objects and existing outlets and actions in the nib file or storyboard .
When you create a new Mac OS X application or iOS view-based project, Xcode includes a nib file for your main
view and a view controller class. When you create a new iOS storyboard-based project, Xcode includes a
storyboard and a view controller class. The view controller is represented in the nib file as the File’s Owner


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object. When you need a new nib file for a project, you should create the interface and implementation files
for the controller first. In many cases, Xcode creates a nib file as well. As nib files usually have controllers already
assigned to them, it is rarely necessary to add a separate view controller to a nib file.

Add a New Nib File
When you need a new nib file, first add interface and implementation files for the controller to the project. In
some cases, you automatically get a new nib file as well. If not, you can then add a nib file and link it to the
controller.

To add a new nib file to a project
1.

Choose File > New > New File and select the template type for your new controller files.

2.

Click Next and specify the name and parent class of the new controller.


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In the figure, for example, the new class will be a subclass of NSWindowController named
MyWindowController.

3.

Click Next, specify the location for the new files, and click Create. Xcode creates a header file and an
implementation file and adds them to your project.
In some cases, such as if you add a controller that’s a subclass of NSViewController, you automatically
get a nib file as well. If so, skip to step 5.

4.

Add a nib file by choosing File > New > New File and selecting a User Interface template in the New
File dialog.


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The following figure shows a Mac OS X user interface file of type Window being selected in the New
File dialog.

Tip: Be sure you select the appropriate file type for the correct platform. For example, there
are two nib templates named Application: one for iOS, and one for Mac OS X.


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5.

Open the new nib file by selecting it in the project navigator so that it appears in the Interface Builder
editor.

6.

Select the File’s Owner object in the Interface Builder dock and choose your controller in the class field
under Custom Class in the Identity inspector.
If your nib file was added automatically by Xcode, it will probably already be set to the appropriate
controller, but you should check to be certain.

Tip: Instead of using the New File dialog, you can drag controller and interface files from the File Template
library into the project navigator. When dragging into the project navigator, be sure the group into which
you want to drop the file is highlighted before you drop; you won’t get the results you want if you accidentally
drop the file inside another file.

To see the outlets and actions provided by the parent class of the File’s Owner, click the File’s Owner object
in the dock and open the Connections inspector. To add new actions or outlets to the nib file’s controller, see
"Make Connections Directly Between IB Objects and Your Code Files" (page 107).


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Add a Custom View
A custom view is a new subclass of one of the standard views used by Interface Builder, such as NSView or
NSButton. To add a custom view, first create the view’s class in the project navigator, then add the view to
your nib.

To add a custom view to a nib file
1.

Create header and implementation files for the view by choosing File > New > New File and selecting
the Objective-C class template. Be sure to choose the appropriate parent class in the “Subclass of”
pop-up menu.

2.

Drag a custom view object from the library into the nib file.

3.

Select the custom view and assign the correct class to it in the class field under Custom Class in the
Identity inspector (see step 3 of "To add a new nib file to a project" (page 98)).
If your custom class doesn’t appear in the pop-up menu, you can type it in.


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Add a New Controller
Every nib file is created with a File’s Owner object, which you link to the controller for the file. In the rare event
that you need to add another controller to a nib file (to control a subview, for example), you need to create
source files for the controller and add a controller object to the nib file so that you can make connections to
the controller.

To add a controller to a nib file
1.

Create header and implementation files for the controller by choosing File > New > New File and
choosing the Objective-C class template with NSObject in the “Subclass of” pop-up menu.

2.

Drag the Object object from the Object library in the utilities pane into the dock of your Interface
Builder nib file.
Tip: Type nsobject into the search field to find the object quickly.


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Simultaneously Design and Implement User Interface Objects Using Multiple Editors

3.

Use the class field under Custom Class in the Identity inspector to assign the class of your controller
to the object.

4.

Use the Label field in the Identity inspector to assign a display name to your controller object.

To see the outlets and actions provided by the controller, click the controller object in the dock and open the
Connections inspector. To add new actions or outlets to the controller, see "Make Connections Directly Between
IB Objects and Your Code Files" (page 107).

Simultaneously Design and Implement User Interface Objects Using
Multiple Editors
When you use custom subclasses in your interface, or add outlets and actions to a controller, you can use an
assistant editor pane to work on your interface code at the same time as your UI design.

To use Assistant with Interface Builder
1.

Select your nib file in the project navigator to open Interface Builder.

2.

Select the interface object for which you want to add outlets and actions.

3.

Click the Assistant button to open the assistant editor pane.


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Simultaneously Design and Implement User Interface Objects Using Multiple Editors

4.

If the assistant editor does not automatically display the header file you want, use the assistant editor
pane jump bar to select the source file containing the controller code for the object.

Tip: Choose View > Assistant Layout to select the orientation of the split between the source
and assistant editors.

You can write code for the window controller at the same time you are designing your window, and you can
make connections directly between Interface Builder objects and lines in your code. Figure 4-14 shows a
window object selected in the Interface Builder pane with the assistant editor pane displaying the file
SKTWindowController.m. The oval containing the numerals 4/5 at the right end of the assistant editor jump


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Manage Connections Between User Interface Objects

bar indicates that the fourth of five counterpart files is being displayed (in this case the others are
SKTWindowController.h, SKTGraphicView.h, SKTGraphicView.m, and NSWindow.h). Click the right
or left arrows to display the others in turn.
Figure 4-14

Interface Builder and Assistant

The objects in your user interface must communicate with each other and with your source code if your program
is to interact with the user. To specify which messages are sent and received, you use Interface Builder to create
connections. There are four fundamental types of connections you can create:
●

Outlet connections

●

Action connections (Mac OS X only)


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●

Event connections (iOS only)

●

Bindings (Mac OS X only)

Make Connections Directly Between IB Objects and Your Code Files
You can make a connection directly from an Interface Builder object to the appropriate header or implementation
file, and, if needed, Xcode inserts code directly into your header and implementation files.
Figure 4-15 shows a connection being made to an existing IBAction statement.
Figure 4-15

Making a connection to source code from Interface Builder

Connect an object directly to the declaration of a new outlet in a source file.

To create and connect a new outlet . . .
1.

With a nib file open, click the Assistant button.

2.

In the jump bar, select the header file in which you want to declare a new outlet.

3.

Control-drag from a nib object to the location in the header file for the new outlet.

4.

In the dialog, choose Outlet from the Connection menu.


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5.

Type the name of the new outlet and click Connect.


As you Control-drag from an object to your source code, Interface Builder indicates where a new outlet is
valid. After you enter the name of the outlet, Interface Builder declares the outlet for you and connects the
object to it. You can choose to make the outlet an instance variable or a property.
You may need to add source code that uses the outlet. You can Option-click the name of your controller's
implementation file in the source editor’s jump bar to open the implementation file alongside the header
file.
The video shows connecting an NSMatrix object to a property outlet in a window controller class.
Alternative: Declare the outlet in your source code manually, then connect an object directly
to the outlet declaration.

Connect an object to the declaration of a new action method in a header file.

To create and connect a new action . . .
1.

Choose View > Assistant Editor > Open Assistant Editor.

2.

In the primary editor, open the user interface document that contains the object that invokes the new
action.

3.

In an assistant editor, open the header file to which to add the action-method declaration.

4.

Control-drag from the object to the header file.

5.

Choose Action from the Connection menu.

6.

Enter the name of the action method, and click Connect.



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As you Control-drag from an object to your source code, Xcode indicates where a new action is valid. After
you enter the name of the action, Xcode declares the action for you and connects the object to it.
Xcode also inserts a skeletal definition for the new action in the implementation file. You need to add the
source code that implements the action. You can Option-click the name of the implementation file in the
source editor’s jump bar to open the implementation file alongside the header file.
The video shows connecting a button matrix to a new action in a window controller class.
If you make the connection to a header file, Xcode also inserts code in the corresponding implementation file
as appropriate. For example, if you use Interface Builder to place a new action called loadComposition in a
header file, Xcode inserts the line
- (IBAction)loadComposition:(id)sender;

in the header file and, in the corresponding implementation file, Xcode inserts
- (IBAction)loadComposition:(id)sender {
}

You can then put your implementation code for the loadComposition method directly into the implementation
file.


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Note: Because Xcode 4 parses both your header files and implementation files for indexing, you
can define actions and outlets in implementation (.m) files without needing to place them in the
header file and you can make connections directly from the nib file to the implementation file.
Therefore, you do not need to expose parts of your interface or actions to clients who might be using
your classes.

Note that, because the Control-click key combination is used by Interface Builder to make connections, you
must Control-click on the canvas—not on any object in the user interface—to get the shortcut menu with the
list of help articles for Interface Builder (Figure 4-16).
Figure 4-16

Help articles in Interface Builder

Add Outlets and Actions to Classes Programmatically
The easiest way to add an outlet or action to your controller class is by dragging from an Interface Builder
object, as described in the preceding section. However, in some cases you might want to define certain outlets
or actions in your code before configuring connections in Interface Builder. To do so, you use the IBOutlet,
IBOutletConnection, and IBAction keywords in your code. Because Xcode 4 indexes both header and
implementation files, you can add outlets and actions to the implementation file only so that you do not expose
your connections to clients who use your public header files.


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Use the Inspector or the Connections Panel to Make Connections
You can manage outlet, action, and event connections by using the inspector or the connections panel. These
two tools provide the same basic behavior but do so in slightly different ways. The Connections inspector
displays the connections associated with the currently selected object. Changing the selection changes the
contents of the inspector. The connections panel is an on-demand window that you open by Control-clicking
the object. The connections panel displays the connections for the same object until the panel is dismissed.
You can open multiple connections panels at the same time.
You can use the techniques described in this section to make connections that are already defined in the source
code or system frameworks. To define new outlets, actions, or events, see "Make Connections Directly Between
IB Objects and Your Code Files" (page 107).

To make a quick connection
1.

Control-drag from the source object to the target object. If a connection is possible with the target
object, the target object is highlighted.

2.

When you complete the drag, Interface Builder displays a prospective list of actions and outlets.

3.

Select an outlet (of the source object) or an action or event (of the target object) to create the connection.

When you use the Control-drag gesture to create a connection for an action or event, the final part of the
task involves picking the action or event from a list. Outlet connections display a similar list. If there are
previous connections that have the same name, the menu items to pick those names are flagged. If a
connection identical to the one being made already exists, the menu item is flagged with a dot. If a
connection exists with that name, but to a different object, it is flagged with a dash.
Tip: For action connections in Mac OS X, this technique is equivalent to opening the connections panel and
configuring the source object’s sent actions connection. Because a source object in Mac OS X can send its
action message to only one target object, you should use this technique only once to configure a given source
object’s action connection. Repeating the process for the same source object would break the old connection
before establishing the new one. You can use this technique, however, to configure each of the source object’s
outlets.

To make a connection using the connections panel
1.

Control-click an object and release the mouse button to display the panel.

2.

Drag from the circle to the right of the action, outlet, or event you want to connect to the target object.
If the target of a connection is not visible, holding the pointer over its parent object causes the parent
to open and reveal its children.
If a connection is possible with the target object, the target object is highlighted.


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3.

If you are using the connections panel to configure the sent action or referencing outlet for the object,
when you complete the drag, Interface Builder displays a list of the target object’s action methods or
outlets. Select an action method or outlet from the list to finish the connection.

4.

If you want to select other objects in your nib file but do not want the connections panel to disappear,
drag the panel to a new location.
You do not have to drag the window far; even dragging it a single pixel is sufficient. Note that if you
do this, you must dismiss the window yourself by clicking its close box when you are done.

After you establish a connection, the connections panel fills the circle next to that action or outlet and
displays information about the connection. Each connection also includes a close box icon that you can
use to break the connection. If a received action has multiple source objects associated with it, the panel
displays a disclosure triangle, which you can use to reveal the individual connections. If you select a
connection, Interface Builder displays a path control at the bottom of the panel and a "take me there"
button for the selected connection.
The connections panel remains visible as long as you use it. If you click outside the panel (by selecting a different
object in your window, for example) Interface Builder dismisses the panel automatically to get it out of your
way. You can also dismiss the panel explicitly by clicking its close box.
You can start an action or event connection at the source object to connect from the sent action selector (for
Mac OS X applications) or to connect from an event (for iOS applications). You can start a connection at the
target object to connect one of its action methods to a source object.
When connecting from target to source, you can connect each action method multiple times. After you make
the first connection, the circle next to the action method is filled to show that there is an associated source
object. To connect an additional source object, drag from the circle to the target object. Performing this action
does not remove the original connection.
Like action connections, you can create outlet connections starting at either the source or target object. In
Mac OS X and in iOS 3.3 and earlier, only one object at a time may be connected to a given outlet. In iOS 3.4
and later, multiple objects can be connected to a given outlet.
You can also use the Connections inspector to make and view connections. The Connections inspector provides
a summary of the outlets and actions (or events) of the selected object. You can use the inspector to view the
status of connections, to create new connections, and to break existing connections.

To make a connection using the inspector
1.

Open the Connections inspector and select an object.


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2.

Drag from the circle next to the entry you want to connect to the target object for the connection. (If
the target of a connection is not visible, holding the pointer over its parent object causes the parent
to open and reveal its children.) If a connection is possible with the target object, the target object is
highlighted when you hold the pointer over it.

3.

If you are using the Connections inspector to configure the sent action or referencing outlet for the
object, when you complete the drag, Interface Builder displays a list of the target object’s action methods
or outlets. Select an action method or outlet from the list to finish the connection.

After you establish a connection, the Connections inspector fills the circle next to that entry and displays
information about the connection. Each connection also includes a close box icon that you can use to break
the connection. If a received action has multiple source objects associated with it, the panel displays a
disclosure triangle, which you can use to reveal the individual connections.

Break and Reconfigure Connections
At times you may need to break an existing connection and replace it with a new one. You can use either the
Connections inspector or the connections panel to do so.
Change an object’s connections to other objects in a nib file using the connections panel. After making a
connection directly to your source code, you may need to change or remove the connection. The connections
window shows you all the connections to and from an object, and makes it possible to change or remove
them.

To change a connection . . .
1.

With a nib file open, Control-click an object to open the connections window.

2.

Click the X to the left of the connection name to remove a connection.

3.

Drag from the connection well directly to your source code to add a connection.


The specific connections listed in the connections window depend on the object you select. Types of
connections include Cocoa Touch events, actions, outlets, outlet collections, and bindings. If a connection
exists, the circle on the right (called a connection well ) is filled in and the name of the connected object is
shown.


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Configure Connections Between Model and View Objects

For actions, Cocoa Touch events, and referencing outlets, you can create a connection by dragging from
the connections window directly to your source code. If you’re changing a connection, it’s not necessary
to remove the old connection in order to change it.
The video shows changing an action connection.
Alternative: You can also change an object’s connections using the Connections inspector.

Connect Menu Items to Your Code or Your First Responder
There are two common techniques for handling menu commands in a Mac OS X application:
●

Connect the corresponding menu item to a first responder method.

●

Connect the menu item to a method of your custom application object or your application delegate object.

Of these two techniques, the first is somewhat more common given that many menu commands act on the
current document or its contents, which are part of the responder chain. The second technique is used primarily
to handle commands that are global to the application, such as displaying preferences or creating a new
document. It is possible for a custom application object or its delegate to dispatch events to documents, but
doing so is generally more cumbersome and prone to errors.
Note: In addition to implementing action methods to respond to your menu commands, also
remember to implement the methods of the NSMenuValidation protocol to enable the menu
items for those commands.

Cocoa bindings are a controller-layer mechanism used to synchronize the view and model layers of your Mac
OS X application. Bindings establish a mediated connection (through a controller object) between a view and
a piece of data, binding them in such a way that a change in one is reflected in the other.
One of the advantages of using bindings over traditional glue code is that you can use Interface Builder to
configure them. Objects with bindable properties can expose those properties in Interface Builder. You can
then configure that binding directly using the Bindings inspector. The configured bindings are saved in the
nib file and re-created at runtime like other types of connections.
You configure bindings in Interface Builder by starting at the object that exposes a bindable property—typically,
a view or controller object. You then use the Bindings inspector to specify the target of the binding and the
binding options. You must configure each binding separately and each binding can be attached to a different


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target object. The target of a binding is always one of the recognized controller objects in your nib file, which
typically includes the File’s Owner, the application, the shared user defaults controller, and any custom controller
objects (especially NSController objects) you add to the nib file.
For more information about how Cocoa bindings work, see Cocoa Bindings Programming Topics .
Note: Cocoa bindings are not available in iOS.

Create and Configure a Binding with the Bindings Inspector
In Interface Builder, you typically bind views and controller objects in your nib file to the data in your custom
controller objects.

To create a binding
1.

Create the views needed to display your data.

2.

Create any intermediate controller objects needed to manage your data. (Typical controller objects
include instances of your custom NSDocument or NSWindowController subclasses, NSController
subclasses, or custom NSObject subclasses that you create to manage your data structures.)

3.

Use the Bindings inspector to configure each binding.


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Although each binding displays several configuration options, the most important part of a binding is the
target of the binding. You must configure, at a minimum, the following fields for any given binding:
●

Bind to

●

Model Key Path

The Bind to field specifies the controller object to use as the starting point for accessing the target data.
The Model Key Path field contains a string representing the key path for the data. Key path strings are of the
form <property_name>[.<property_name>]*. The first property name in this string is a property on the
controller object specified by the Bind to field. Each subsequent property name corresponds to a property of
the object returned by the previous property name. Say, for example, that you have a custom controller object
and the key path string “person.address.street“. The person property returns the person object of the
bound controller. The address property returns the address of the corresponding person object. And the
street property returns the data value stored in the address object.

Create a Binding by Dragging Directly to Your Header File
As with outlets and actions, you can drag directly from an object in your nib file to code in your header file to
create a binding.
Bind an object directly to a declaration in a header file.

To create a binding by dragging . . .
1.

With a nib file open, display the Assistant editor.

2.

In the jump bar of the Assistant editor, choose the header file of the object to which you will make the
binding.

3.

Control-drag from a nib object to the symbol in the header file for the new binding.

4.

In the dialog, configure the binding and click Connect.



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As you Control-drag from an object to your source code, Interface Builder indicates where a new binding
is valid. After you’ve made the connection, Xcode displays a dialog you use to configure the binding. You
can use the dialog to configure all aspects of the binding.
Interface Builder uses the Xcode index to determine which key paths are valid, and can also discover what
controller it should connect through—you can therefore connect from a user interface element such as a
table column to a property in a model class header.
Note: If the dock on the left of your Interface Builder editor does not look like the one in the
video, click the button at the bottom of the dock (

) to toggle from outline view to icon view.

Key Paths Are Dependent on Your Data Model
The best way to understand how to bind key paths in Interface Builder is to go through some examples. The
following sections show how to bind a text field to an NSNumber object to display the number value in that
text field. In each successive example, the data model used to access the number value gets progressively
more complex, and so the bindings must be adjusted in accordance with the increased complexity.
For bindings examples, see Cocoa Bindings Programming Topics .

Bind a Document Object Directly to a Value
The simplest key path occurs when you bind your Interface Builder object directly to a data value in your code.

To set up a simple object-data relationship
1.

Set the target object to the document’s File’s Owner.
The document object must be KVC compliant.

2.

Set the model key path to the name of the instance variable.

Bind a Document Object to a Data Object Through an Object Controller
Frequently, the File’s Owner isn't the main data-containing object. Instead, you typically have other data objects
(often held in a collection), referenced by the File’s Owner. In this case, you should add an object controller
(an NSObjectController object) and bind the user interface object (the view object) to the data object
through the controller object and the File’s Owner. The controller object acts somewhat like a buffer layer
between your view and data object and the controller object acts as a placeholder for the document’s current
Entry object, providing a valid binding target even if the document’s entry property becomes nil.


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To bind to a data object through an object controller
1.

Set the target object to the NSObjectController object.
The object controller, document object, and data object must all be KVC compliant.

2.

Choose either selection or selectedObjects in the Controller Key pop-up menu.

3.

Add the target property in the Model Key Path field.
Mac OS X combines the strings in the Controller Key and Model Key Path fields to get the final key
path.

Bind to a Collection of Objects Through an Object Controller
Using controller objects, it is as simple to bind to a collection of objects as it is to bind to a single object. In
fact, the bindings themselves are almost identical. Instead of binding to a single object, you bind the view to
a collection of objects through an NSArrayController object. The array controller manages both the
collection of objects and the list of indexes corresponding to the selected objects and uses that information
to provide an appropriate value to the text field.

To bind to a collection of objects
1.

Bind the text field to an NSArrayController object’s selection property, which represents the
currently selected Entry object.

2.

Specify the quantity string for the key path.

Configure the Binding Attributes to Customize the Binding
Although the Bindings inspector may seem complex at first, for many bindings, you need to configure only a
few options initially. You may not need to configure every option every time (except for the Bind to and Model
Key Path fields). During your initial design phase, you can probably leave most of the options configured with
their default values. As you improve your design, you can customize the options more until you have the
behavior you want.
For a complete list of bindings available for a given view or controller object, see Cocoa Bindings Reference .

Bind to Objects in a Custom Tree Data Structure
If your program contains a custom tree data structure, you can use an NSTreeController object to coordinate
bindings to the objects in that data structure. Tree controllers are often used to bind data objects to an
NSBrowser or NSOutlineView object in order to display hierarchical sets of data to the user.


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To configure a tree controller object
1.

Add the tree controller object to your document and select it.

2.

Open the Attributes inspector.

3.

Fill in the Object Controller section.
●

●

4.

In the Class Name field, specify the class name of the objects in the tree.
Optionally, specify any custom keys of the tree objects that you want to expose in the Model Key
Path field of the bindings inspector.

Fill in the Tree Controller section.
●

●

●

In the Children field, specify the key path for the property that identifies the child nodes of a given
tree object.
In the Count field, specify the key path for the property that indicates how many children a given
tree object has. (This key path is optional.)
In the Leaf field, specify the key path for the property that identifies whether the current tree
object is a leaf node. (This key path is optional but recommended because it can improve the tree
controller’s performance as it navigates your tree at runtime.)

For more information on using tree controllers, see Cocoa Bindings Programming Topics .

Bind to Your Application Preferences
An NSUserDefaultsController object is most often used when implementing a preferences window or
in any situation where you want to bind a view to values in the defaults database. Although you can add a
new NSUserDefaultsController objects to your nib file, you generally do not need to do so. Interface
Builder provides a shared user defaults controller object that you can use to bind to your application’s
preferences.

To use the shared defaults controller to implement your application’s preferences window
1.

Select the control you want to bind to a preference.

2.

Open the Bindings inspector.

3.

In the appropriate binding for your control, set the Bind to field to Shared User Defaults Controller.

4.

In the Model Key Path field, enter the key name of the preference you want to associate with the
control.


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Tip: By default, the shared user defaults controller sets the value in the Controller Key field to "values” Because
.
individual preference values are accessed through this property on the user defaults controller, you should
leave this field configured as is.

For more information on configuring user defaults bindings, see "User Defaults and Bindings" in Cocoa Bindings
Programming Topics .


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You write and edit code with the Xcode source editor, which has many professional-level features, such as
automatic formatting, code completion and correction, and online documentation. You can discover most of
these features by looking in the Edit and Editor menus as well as Control-clicking in the editor to see the
contextual menu. This chapter briefly reviews the features you are likely to use most often and describes some
features that you might not discover easily by yourself.
In addition to writing and editing code in the source editor, you can set breakpoints, view the values of variables,
step through running code, and review issues found during builds or code analysis. These features are part of
the debugging and build-run workflows, and so are discussed in other chapters (see "Debug Your App" (page
180) and "Configure Your Project" (page 66)).

Customize the Source Editor with Xcode Preferences
Here are some of the ways you can customize both the appearance and function of the source editor in Xcode
preferences by using the Fonts & Colors, Text Editing, and Key Bindings panes.

Modify Syntax-Aware Fonts and Text Colors
Xcode parses code based on the language (as determined from the filename extension) and assigns a syntactic
label to each token or string: comment, keyword, class name defined in the project, other class name, and so
forth. By default, Xcode assigns a color and font to each syntactic type to make it easier for you to read the
code. Xcode Fonts & Colors preferences allows you to select among several font and color themes; for example,


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the Presentation theme increases the font sizes so that the text is easier to read when projected on a screen.
You can also create your own custom font and color theme. For example, in Figure 5-1, symbols defined in the
project are given a distinct color to make them easier to pick out.
Figure 5-1

Fonts & Colors preferences

Customize the appearance of source code and console text by changing their colors and fonts in Fonts &
Colors preferences. For example, you could display your code comments in purple in the source editor. For
the console, you could set your debugger input and your debugger output to a 14-point font.

To set font and color preferences . . .
1.

Choose Xcode > Preferences and click Fonts & Colors.

2.

Click either Source Editor or Console near the top of the preferences window.

3.

Select a theme.

4.

Select a syntax category.

5.

To change the font, click the Fonts window button, and make your selections in the Fonts window.


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6.

To change the text color, click the font color well, and choose a new color in the Colors window.

7.

To change the color of other items in the source editor or console, click a color well at the bottom of
the pane, and choose a new color.

The source editor’s Comments category for the Default theme is selected in the screenshot. A theme includes
preset colors and fonts for all the syntax categories. Xcode includes a set of standard themes, such as Default,
that you can modify or delete. You can restore any of the standard themes by selecting from a set of
templates that are displayed when you click the Add (+) button at the bottom of the theme list.
For the source editor and the console, you can also customize colors for the:
●

Background

●

Selection

●

Cursor

●

Instruction pointer (for the console)

Tip: You can change the font or font size for all the syntax categories in a theme. Select a category,
press Command-A to select all categories, and modify the settings for the font or font size.

Customize the keyboard shortcut for a command by editing its key sequence in the Key Bindings preferences
pane.

To customize keyboard shortcuts . . .
1.

In the Key Bindings preferences pane, choose a command set to edit.

2.

Locate the command for which you want to change the shortcut.


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3.

Double-click a key sequence to select it.

4.

Type a new key sequence to replace the selected one.

5.

Click elsewhere in the detail area to apply your change.


To edit the key binding for a command, double-click its key field, and then:
●

●

●

●

To change a selected sequence, type a new one to replace it.
To remove a selected sequence, click the Remove (—) button. (Do not press the keyboard Delete key;
that just adds Delete to the key sequence.)
To enter a sequence in an empty key field, type the sequence.
To add a sequence to an existing one, click the Add (+) button and type the new sequence. This only
works for text commands; you cannot assign more than one sequence to a menu command.

Important: When you have made your changes, be sure to click outside the key field to close it. Pressing
any key while the field is open changes the key sequence.
Specify a key sequence by typing it just as you would type it to use it; for example, to specify ^A, hold down
the Control key and type the letter a.
A specific key sequence can be bound to only one command; if you enter one that is already assigned to
another command, Xcode removes it from that other command.
The video shows adding the key sequence Control-Option–Right Arrow as a shortcut for the Move Expression
Right command.
For detailed information about key bindings, see “Text System Defaults and Key Bindings” in Cocoa
Event-Handling Guide .


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Enter Code Quickly and Accurately with the Help of the Source Editor

Set Your Text-Editing and Automatic Indentation Preferences
You can set several preferences that control the appearance and behavior of the source editor—including
whether line numbers are displayed, how delimiter balancing and the code focus ribbon work, and some
aspects of code completion—in the Editing pane of Text Editing preferences.. You can control many of the
automatic-indenting features of the editor in the Indentation pane of Text Editing preferences. Control-click
in either pane to see a help article that describes the use of the fields.

The source editor includes several features that help you enter code and avoid mistakes:
●

Code completion

●

Quick Help

●

Automatic delimiter balancing

●

Automatic indenting

●

Syntax formatting

●

Fix-it

Speed Up Typing with Code Completion
When you begin typing the name of a symbol that Xcode has indexed, it offers an inline suggestion for
completing the symbol name plus a list of possibilities (Figure 5-2). Click an item in the suggestion list or use
the Up Arrow and Down Arrow keys to select one. As you do so, the inline suggestion changes as well.


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Furthermore, as you can see in the figure, if you open the Symbol inspector in the utility pane, you can read
documentation about each selection. You can turn off automatic code completion in the Text Editing pane of
Xcode preferences, but you can always invoke code completion by pressing Control–Space bar or Esc.
Figure 5-2

Code completion

Finish entering a symbol by accepting an Xcode suggestion for completion. The proposed symbol is based on
the text you have typed so far and the surrounding context. Continue typing to refine the list of choices.

To enter text with code completion . . .
1.

Begin typing the name of a symbol.

2.

Click an item in the suggestion list.

3.

Press Return to accept the suggestion.


If all of the possible completions have a common prefix, the prefix is indicated with a dotted underline.
Press the Tab key to accept only the prefix, or press Return to accept the entire suggestion.


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Press Control–Space bar to toggle the completion suggestion on or off. That is, if the inline suggestion and
list are being displayed, pressing Control–Space bar cancels the code completion operation. (Pressing the
Esc key or clicking elsewhere in the text also cancels the operation.) If there is no suggestion displayed,
place the insertion point at the end of a partially-typed symbol and press Control–Space bar to get completion
suggestions.
To turn off the code completion feature, choose Xcode > Preferences and click Text Editing. In the Editing
pane, deselect the option “Suggest completions while typing.” You can always invoke code completion by
pressing Control–Space bar.
A Quick Help pop-up window is available from code completion. Hold the pointer over the code completion
option you’re interested in until a question mark icon appears. Click the question mark to open Quick Help.
As before, press the Tab key to accept the prefix or Return to accept the entire suggestion. Click the Done
button in the Quick Help window to close the window.
When a method or function contains parameters or arguments, code completion includes a placeholder
for each. Choose the Jump to Next Placeholder (Control-/) and Jump to Previous Placeholder (Control-Shift-?)
items in the Navigate menu to move from one placeholder to another.


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Note: The code completion feature is not fully functional until Xcode finishes indexing your
project.

Code completion inline quick help is shown in Figure 5-3. Code completion placeholders for parameters are
shown in Figure 5-4.
Figure 5-3

Quick Help for code completion

Figure 5-4

Placeholders in code completion text

Balances Delimiters Automatically
When you create a new file or edit an existing one, Xcode determines the source language from the filename
extension and attempts to determine the syntax of the text based on the source type. For example, a file with
a .h or .m extension is assumed to be a variety of C and formatted accordingly. In that case, the editor indents
the text according to the rules you set in Text Editing preferences and uses fonts and colors for the various
syntax elements (variables, constants, comments, and so forth) according to the settings in the Fonts & Colors
pane of Xcode preferences.
When you’re writing code, type an opening brace ({), and continue typing, Xcode automatically adds a closing
brace (}) unless you’ve deactivated this feature in Text Editing preferences. There are several other features
that help you to balance delimiters, including double-clicking a delimiter to select the entire expression.

To get assistance in balancing delimiters


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●

Type an opening brace.
Xcode automatically inserts a closing brace after you enter a line break. (If you don’t want closing braces
automatically inserted, choose Xcode > Preferences, click Text Editing, and deselect “Automatically
insert closing ‘}’”
.)

●

Use the Right Arrow key to move the insertion point past a closing delimiter.
Xcode briefly highlights its counterpart.

●

Double-click any delimiter.
Xcode selects everything up to and including the matching delimiter.

●

Position the pointer over the focus ribbon.
Xcode highlights the scope at that location.

●

Type a closing brace or other delimiter.
Xcode causes its counterpart to blink.

●

Choose Editor > Structure > Balance Delimiter.
Xcode selects the text surrounding the insertion point, up to the nearest set of enclosing delimiters.

Have Fix-it Flag Errors as You Type
When your target is set to use the LLVM compiler, a feature called Fix-it scans your source text as you type.
Correct mistakes with Fix-it as you enter source code.

To catch mistakes with Fix-it . . .
1.

In a target built with the LLVM compiler, open a source file.

2.

Introduce an error in the code.

3.

When a red underbar or a caret appears, click the symbol in the gutter to see the error message.

4.

If Fix-it suggests corrections, select a correction and press Return.



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Find and Display Related Content

Fix-it scans your source text as you type. Fix-it marks syntax errors with a red underbar or a caret at the
position of the error, and a symbol in the gutter. Clicking the symbol displays a message describing the
possible syntax error and, in many cases, offers to repair it automatically. Select a suggested correction and
press Return to accept it. Press Esc to cancel the operation.
To use Fix-it, you must build the target with the LLVM compiler and the indexing of your project must be
complete. Fix-it works with the C, Objective-C, and Objective-C++ languages.
The video shows correcting a double equals sign in an assignment statement.
Tip: If there are several Fix-it warnings in a file, you can navigate to the next or previous warning
by choosing Navigate > Jump to Next Issue or Navigate > Jump to Previous Issue.

Xcode provides several features that help you find content related to the code you’re currently editing: you
can open a file based on a partial string, you can jump to a symbol definition, you can navigate to related
content using a button in the jump bar in the primary editor or in a split editor, or you can split the editor and
have Assistant find related content for you.

Open a FIle Quickly
Sometimes you may need to open a file whose location you don’t know, or you may want to open the file that
defines a particular symbol, such as a variable, method, or class. The Open Quickly command finds files that
define a specified symbol or whose filename contains a specified string. Open Quickly searches are case
insensitive and limited to the current project and the active SDK.

To use the Open Quickly command
1.

Choose Open Quickly from the File menu.

2.

In the search field, type any portion of the name of the file you want to open or the symbol you want
to find.


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Tip: Select a filename or symbol name in the editor and invoke the Open Quickly command
to prefill the dialog’s search field with the selected text. Or, to open a header file referenced in
a #include or #import statement, place the cursor on the line of the statement and invoke the
Open Quickly command to search for the header file.
3.

From the search results list, double-click the file you want to open, or select the file you want to open
and click Open.

Tip: To open the file in the assistant editor, hold down the Option key when you double-click
or click Open. To open the file in a separate window, hold Option-Shift. To see a dialog letting
you specify where the file should open, hold down Option-Shift-Click. You can change these
behaviors in the General preferences pane.

In filename-based searches, Xcode searches for header files, implementation files, model files, nib files, plist
files, and project packages. In symbol-name–based searches, it searches source code files only.


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Split the Editor Area to Display Related Content
Xcode allows you to split the editor pane to provide multiple views of the same file or to view multiple files at
once.
To split the editor, open an assistant editor pane by choosing View > Editor > Assistant or by clicking the
Assistant button in the workspace toolbar (Figure 5-5).
Figure 5-5

The Assistant button

To see the same file in each pane
1.

Open an assistant editor pane.

2.

Select Manual from the Assistant pop-up menu ("To set the behavior of the assistant editor" (page
138)).


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You can view any portion of the file in either split plane, and you can edit the file in either pane. Any
changes made in one pane are instantly reflected in the other.

The split can be horizontal (as shown in the figure) or vertical. To change the orientation of the split,
choose View > Assistant Layout.


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Customize Keyboard Shortcuts to Determine Where a File’s Contents Are Displayed
Selecting a file in the project navigator or jump bar causes that file to open in the normal editor pane. If Assistant
is set to tracking mode, it tracks the change. By default, if you hold down the Option key when selecting a file
in the project navigator or jump bar, Xcode displays that file in the Assistant pane rather than the standard
pane. Doing so switches Assistant to manual mode.
You can customize the behavior of the single click, Option-click, and double-click keyboard shortcuts in the
General pane of Xcode preferences (Figure 5-6).
Figure 5-6

General preferences

To customize the behavior of keyboard shortcuts for opening a file, open General Preferences and choose an
option from each navigation pop-up menu. The options include:
●

Primary editor: Opens the file in the primary editor pane in the window and tab already open.

●

Focused editor: Opens the file in whichever editor pane currently has focus.

●

Single assistant editor: When the navigation originates in a navigator pane or the primary editor (using
the jump bar or the jump to definition command), if the assistant editor is not open or is not split, opens
the file in the assistant editor.


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If the assistant editor is split, displays a navigation chooser dialog (Figure 5-7) showing the current layout
of editor panes in the window that has focus, with the option of selecting any open editor pane or adding
a new one. Double-click your selected pane, or make your selection and press Return. Press Esc to cancel.
Figure 5-7

The Single Assistant navigation chooser dialog

If the file is already open in one of the editor panes, the navigation chooser displays a star to indicate the
pane containing the file.
When the navigation originates in an assistant editor pane, Xcode opens the file in the primary editor.
●

Separate assistant editor: If the assistant editor is closed and is not split, opens the file in the assistant
editor.
If the assistant editor is open, opens the file in a new assistant editor pane.
If the assistant editor is split but closed, opens the file in the most-recently-opened assistant editor pane,
replacing the file that was in that pane.
If the file is already open in an assistant editor pane, switches the focus to that pane.

●

Separate tab: If the file is not already open in the current window, opens the file in a new tab.
If the file is already open in another tab in the same window, switches the focus to that tab.

●

Separate window: If the file is not already open in a separate window, opens the file in a new window.
If the file is already open in a separate window, switches the focus to that window.


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The Option-Shift-Click key combination opens a navigation chooser dialog (Figure 5-8 (page 136)) showing the
current layout with the options of selecting any open editor pane in any window and any tab, or adding a new
editor pane, window, or tab. Double-click your selection, or make your selection and press Return. Press Esc
to cancel.
Figure 5-8

The navigation chooser dialog

Jump to a Symbol’s Definition
You can jump to the definition of a symbol and display it in the primary editor window, in a split editor pane,
in another tab, or in another window.

To jump to a symbol’s definition
1.

Hold down the Command key., and command-click the symbol in which you’re interested.


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2.

Move the pointer over text to highlight each symbol that can be used as a link to a definition.

3.

If there is more than one definition for the symbol, Xcode displays a list of possibilities. Click the one
you want.

Alternatively, select the symbol in which you’re interested and choose Navigate > Jump to Definition or
Control-click the symbol and choose Jump to Definition from the shortcut menu.
Tip: Use one of the modifier keys set in the General pane of Xcode preferences together with any of the
methods described here to open the definition in a split editor pane, a tab, or another window.


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Find Related Items with the Jump Bar
Use the related items pop-up menu in the jump bar (Figure 1-19 (page 39)) to jump to files and classes related
to the file you have open. For example, you can find superclasses and subclasses of the class defined in the
open file, headers included in the file, or headers that include the file. For a header file you can jump to the
implementation file, and vice versa.

Find Related Content Automatically
When you open an assistant editor pane, you can set Assistant to either of two modes: tracking (or automatic)
mode or manual mode. Tracking mode has several criteria from which you can choose, such as counterparts,
superclasses, subclasses, or siblings. Assistant selects the file or files that best meet the selected criterion and
opens those files in the assistant editor pane. In manual mode, you select the file to display by navigating to
it in the jump bar. You can split the assistant editor into as many panes as you wish.

To set the behavior of the assistant editor
1.

Open an assistant editor pane.

2.

Open the Assistant pop-up menu. The Assistant pop-up menu is the first item to the right of the back
and forward arrows in the assistant editor jump bar.

3.

Make a selection from the menu.

Tip: The choices offered in the Assistant pop-up menu depend on the type of file being edited.


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To split the assistant editor
1.

Click the plus sign at the right end of the assistant editor jump bar to split the editor.

2.

Set each Assistant pane to manual or tracking.

3.

Set each tracking pane to a tracking criterion.
The figure shows one file on the left of the split editor pane, the counterpart file in the upper-right
Assistant pane, and another view of the file in the lower-right Assistant pane.

Tip: To change the orientation of the split editor panes, choose View > Assistant Layout.


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Use Assistant with Interface Builder and Data Models
When you’re using Interface Builder to design a user interface, you can use Assistant to automatically display
the code file most relevant to the interface element you’re working with. See "Simultaneously Design and
Implement User Interface Objects Using Multiple Editors" (page 117) for details. Similarly, when you use the
Core Data modeling editor, the assistant editor can display model classes related to the entities in your model
(Figure 5-9). The Core Data modeling editor is discussed in "Design Data Models Graphically" (page 26).
Figure 5-9

The assistant editor used with a data model


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Incorporate Other Source Editor Features into Your Workflow

The source editor provides many features to make it easier to write and maintain your code. This section
highlights a few of these features not described elsewhere in this document.

Examine the Structure of Your Code with Code Folding
One powerful way to examine the structure of source code is to use the focus ribbon, also called the code
folding ribbon .
Focus your attention on a particular method or function in source code by hiding the other parts of the source
code.

To fold and unfold source code . . .
1.

With a source file open, click anywhere in the source code.

2.

Choose Editor > Code Folding > Fold Methods & Functions.

3.

Navigate to the method you want to unfold.

4.

Double-click the ellipsis button to unfold the method.

5.

Use the focus ribbon to select the method’s scope.

6.

Click in the focus ribbon to fold the method.


The Code Folding submenu provides several options for folding and unfolding code.
The focus ribbon is located between the editor gutter and the source code. Move the pointer into the focus
ribbon to display a scope in the focus box. Then click in the focus ribbon to fold the code in scope.
The video shows the steps for folding all the methods and functions in the source code, unfolding the
method naturalSize, and folding the same method using the focus ribbon.


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If you have the option “Focus code blocks on hover” selected in Text Editing preferences, then you can move
the pointer over the focus ribbon to examine the various scopes of code blocks in a file. In Figure 5-10, for
example, the pointer is over the focus ribbon next to an if statement and three scopes are indicated by
degrees of shading in the code: the if statement, the method (showOrHideWindow) containing the if
statement, and the class implementation (NSWindowController(SKTConvenience)) containing the method.
Figure 5-10

The focus ribbon in use


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View Preprocessor or Assembly Output
You can use commands in the Product > Generate Output menu to process source files and generate the
preprocessed output (Figure 5-11) or assembly output.
Figure 5-11

Preprocessor output

The preprocessor evaluates directives in your source code (instructions starting with the pound sign (#) such
as includes, defines, and conditional logic) and converts them into C code to be sent to the compiler. You can
examine the preprocessed output to make sure that the logic in your source code is being interpreted by the
preprocessor as you expect in order to debug compilation problems.
The assembly output is the set of instructions that the compiler generated from the preprocessed output. You
can study the assembly output to see how the instructions were formed or ordered, to seek out better
optimization patterns, or to look for compiler bugs.


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The output type is also a new category in the assistant editor for a selected primary file (Figure 5-12).
Figure 5-12

Generated output in Assistant jump bar

View Documentation for a Symbol Using Quick Help
You use Quick Help in the Symbol inspector to get information about API symbols, user interface objects, and
build settings.
Find concise reference documentation for an API symbol without moving away from your source file.

To look up documentation for an API symbol . . .
1.

With a source file open, click the Symbol inspector button in the utility area.

2.

Place the insertion point in an API symbol in the source editor.

3.

View the documentation under Quick Help in the Symbol inspector.

4.

To view more detailed information, click the API name at the top of Quick Help.



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When you place the insertion point in a symbol, summary reference information appears in the Symbol
inspector in the utility area.
The information includes links to:
●

Complete reference documentation for the symbol

●

The header file where the symbol is declared

●

Related programming guides

●

Related sample code

Alternative: To view concise reference information for an API symbol in a pop-up window,
Option-click the symbol in the source code.

To get information about a symbol when the utility area is closed, you can open a Quick Help window by
Option-clicking the symbol (“Find and Display Related Content”).
Figure 5-13

The Quick Help window

Find concise documentation for an object using Quick Help. You can find concise class reference documentation
for a single object without taking your focus away from your nib file.

To look up documentation for an Interface Builder object . . .
1.

With a nib file open, click the Quick Help button.

2.

Click the object about which you want information.

3.

View the documentation under Quick Help.


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4.

To view more detailed information, click the title of the reference document.


Quick Help offers a persistent location for API reference documentation. When you click an object, Quick
Help displays information about that object.
For complete reference information about the object, click the title of the reference document listed in
Quick Help. The reference document opens in the Organizer window. You can also open relevant
programming guides, sample code, and other related documents by clicking their titles in Quick Help.
Find concise documentation for a build setting using Quick Help.

To look up documentation for a build setting . . .
1.

Click Build Settings at the top of the project editor.

2.

Display the Symbols inspector.

3.

Select a build setting.

4.

View the documentation under Quick Help in the Symbols inspector.


Quick Help provides a persistent location for build setting documentation without taking your focus away
from the build settings pane. Whenever you select a build setting, Quick Help displays information about
that item.
The video shows viewing information on a build setting in Sketch.


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Alternative: Option—double-click a build setting to open Quick Help in a separate window.
Unlike Quick Help in the utility area, the Quick Help window is not persistent.

Automate Extensive Changes in Your Files
In addition to all the features Xcode provides to make it easier to enter and correct your code, there are features
at several scales to help you make changes that apply to more than one line of text. These include Edit All in
Scope, Search and Replace, and Refactor.
Simultaneously modify all the occurrences of a symbol within a scope with the Edit All in Scope feature. For
example, you can change the name of a local variable or parameter everywhere in a scope at the same time.

To edit a symbol everywhere in a scope . . .
1.

Place the insertion point in the symbol you want to edit.

2.

When the pop-up menu appears, select Edit All in Scope.

3.

Edit the symbol.


Placing the insertion point in a symbol underlines all occurrences of that symbol in the scope and lets you
see the extent to which it is used.
Choosing Edit All in Scope from the pop-up menu selects all occurrences of the symbol. As you type new
text, all selections of the symbol change simultaneously.
The video demonstrates changing the symbol lowerRight to lowerRightCorner within the alignedRect
method.
To find and change all the instances of a text string in a single file, choose Edit > Find > Find and Replace.
To find and change all the instances of a text string in your project or workspace, use the Replace option of
the search navigator (see "Replace Text Strings" (page 215)).
To refactor code (that is, to change the code without changing its behavior), see "Improve Your Code’s Structure
Through Refactoring" (page 221).


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Incorporate Files and Code from the Xcode Libraries
Xcode provides libraries of file templates and code snippets that you can use in your program. It also has
libraries of Interface Builder objects and media files that you can use in your nib files. The library pane is in the
lower part of the utility area (see “The Xcode 4 workspace window” (page 12)). Each of the buttons at the top
of this pane selects a category of library objects, as follows:
●

●

●

●

File templates range from templates for applications to subclasses of commonly used Cocoa classes. File
templates have subcategories, which you can choose from the pop-up menu below the line of buttons.
You can display the templates as icons only or as icons and text. Drag file and project templates to the
project navigator.
Code snippets are short pieces of source code that you can use in your software. To use one, drag it
directly into your source code file. Alternatively, you can select a portion of the code from the code
information pop-up window and drag that into your file. When you create a code snippet, you can add a
completion shortcut, which you can use when editing source code. Type the shortcut and select the
completion shortcut from the completion list to add the code snippet to your file. Note that the new code
snippet is flagged with the word “User”
.
Interface builder objects are organized with subcategories and provide information pop-up windows
like those for the file templates and code snippets. Depending on the object, you drag it onto the Interface
Builder canvas, into another object on the canvas, or into the Interface Builder dock. See "Edit User
Interfaces" (page 76) for more information on Interface Builder.
Media files include all the graphics, icons, sound files, and other media files that you use in your code.
When you’re editing an Interface Builder document, the Media library also shows the built-in template
images from NSImage and sounds provided by the system. In Interface Builder, you can drag an image
from the library and drop it into your user interface. Interface Builder creates an image view to hold the
dropped image. Alternatively, you can drag an image into an existing button, image view, or any other
object that can contain an image. You can set a sound on an NSButton object.

Add a new file to a project or workspace using the File Template library. This library offers a convenient way
to create files in your project or workspace.

To add a new file from the File Template library . . .
1.

Choose File Template Library from the Utilities menu under the View menu.

2.

Select the file template in the library.

3.

Drag the template to a project or group in the project navigator.


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Edit Source Code

4.

Name the file, and click Save.


The video illustrates using a template from the File Template library to add an Objective-C class to a project.
Note that the library button is labeled with a file icon.
Using the provided file templates ensures that certain minimal file characteristics are correct for a file. For
example, as seen in the video, Xcode automatically creates both the implementation (.m) file and the header
(.h) file for the new Objective-C class.
When you click a template, an information window pops open with information about the use of the template
(Figure 5-14).
Figure 5-14

A file template information pop-up window

Add frequently-used source code to your project by using a snippet from the Code Snippet library.

To drag a code snippet to a source file . . .
1.

With a source file open, click the Code Snippet library button.

2.

Select a code snippet.


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Edit Source Code

3.

Drag the snippet to the source file.


The system-supplied snippets in the library are designed to speed development and help ensure code
integrity. You can also create custom code snippets.
The video illustrates using a code snippet to add an init method to the implementation of an Objective-C
class.
Extend the scope of the Code Snippet library by creating custom snippets. The Code Snippet library provides
a number of useful standard snippets. You can add to this collection by creating your own custom snippets.

To create a custom code snippet . . .
1.

Open the Code Snippet library.

2.

Select some text in a source file and drag it to the library.

3.

Open the new custom snippet and click Edit.

4.

Give the snippet a name and click Done.


Code snippets let you enter source text with minimum effort. You can drag a standard or custom code
snippet into a source file. You can also type a completion shortcut to enter a snippet.
Tip: You can include tokens in a custom snippet. For example, the string <#Code#> adds a token
labeled Code in the source text created by the snippet.
Enter source code text with minimum effort by typing a completion shortcut for a code snippet.


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Edit Source Code

To determine the shortcut for a code snippet . . .
1.

In the Code Snippet library, select the snippet for which you want to use a shortcut.

2.

Click Edit.

3.

In the Completion Shortcut field, note the shortcut or add one.

4.

Click Done.

Code snippets let you quickly enter source code. You can drag a snippet from the Code Snippet library into
a source file. Or, for maximum efficiency, type a snippet shortcut in the text of your source code, then press
Esc and then Return to enter the snippet. In most cases, when you begin typing the snippet’s completion
shortcut, Xcode suggests it, so you need only accept it by pressing Return. Both standard and custom code
snippets support completion shortcuts. You can edit the shortcut for a custom snippet.
The screenshot shows a completion shortcut highlighted.
Filter the library items displayed in the selected library by entering text into the search field at the bottom of
the library pane.


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Edit Source Code

Use Inspectors to View and Enter Data
Inspectors are panes in the utility area that you can use to read or enter data about files, Interface Builder
objects, symbols, and data models. Figure 5-15 shows the File inspector.
Figure 5-15

The File inspector

The Symbol inspector is discussed in "View Documentation for a Symbol Using Quick Help" (page 144). The File
inspector and Symbol inspector are always available. Other inspectors appear when appropriate. For more
information about Interface Builder, see "Edit User Interfaces" (page 76).


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Build and Run Your App

To build and run your app, Xcode uses the settings in your project and information in a build plan known as
a scheme .

Create, Edit, and Manage Schemes
In Xcode, before you build, you select a scheme, which specifies which targets to build, what build configuration
to use, and the executable environment to use when the product specified by the target is launched. You also
select a run destination. When you create a new Mac OS X project, Xcode provides a default scheme and two
run destinations: local 32-bit and local 64-bit. For an iOS application, the run destinations are devices and
simulators.
You can add as many additional schemes as you want. For example, you might want one scheme that builds
both your application and a plug-in before running, and another that builds the product without the plug-in.
Or if you have two different but commonly used Instruments templates, you might have one scheme for
profiling with one of the templates and a different scheme for the other one.
You use the Scheme pop-up menu in the upper-left corner of the workspace window (“Add Build Configurations”)
to select a scheme and run destination. Choose the scheme you want to edit and then choose Edit Active
Scheme from that menu to edit an existing scheme. Choose Manage Schemes to change the list of schemes,
where they’re stored, and whether they’re shared. Choose New Scheme to add a scheme to your project.
Alternatively, you can choose Edit Scheme, New Scheme, or Manage Schemes from the Product menu.
Figure 6-1

The Scheme pop-up menu


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The left column of the scheme editing dialog (referred to hereafter for brevity’s sake as the scheme editor ) has
a list of actions you can perform, plus the Build item, which you use to determine which targets are built for
each type of action. Each action can be set to produce either a debug or release build (or, if you’ve added more
build configurations, those are listed as well). There are options for building, running, testing, profiling (using
Instruments), analyzing, and archiving your products.
You can execute scripts and have Xcode send emails before or after a build or any of the actions in the scheme
editor.

To set up pre- or post-actions
1.

In the scheme editor, open the disclosure triangle next to Build or any of the actions in the left pane.

2.

Click the Add button at the bottom of the right pane and choose New Run Script Action or New Send
Email Action.

3.

In the template that opens, fill in the fields.
The figure shows two pre-run actions: an email that’s sent and a script that’s executed before the
product is launched.


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4.

For a Run Script pre-or post-action, if your script needs to access values from target build settings,
choose the target from the “Provide build settings from” pop-up menu.

Specify Which Targets Are Built for Each Type of Action
By default, Xcode creates one scheme per target in your project or workspace, and the Targets column shows
the target for which the scheme was created. However, you can add as many targets from your project or
workspace to a single scheme as you wish.
Edit a scheme to determine which targets are built when you choose Run, Test, Profile, Analyze, or Archive
from the Product menu.

To build multiple targets . . .
1.

From the Scheme toolbar menu, choose a scheme.

2.

From the same menu, choose Edit Active Scheme to display the scheme dialog.

3.

In the left column, select Build.

4.

For each target, select the actions for which to build the target.


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5.

Click OK.

Targets which are required due to their use in the Run, Test, or Profile actions cannot be turned off.
Select Parallelize Build if you want to build all independent targets at the same time. If you select this option,
the build is faster but it may not produce correct results unless you set up target dependencies correctly.
The Find Implicit Dependencies option is selected by default. Deselect this option if you add a project to
your workspace that you don’t want used automatically.

Rename or Reorganize Your Schemes
By choosing Manage Schemes from the Product menu (or from the Scheme pop-up menu) you can see a list
of all the schemes in the project. You can rename or reorganize the schemes in the menu. You can also specify
whether each scheme should be displayed in the pop-up menu, where the scheme is stored (in the project or
workspace) and whether the scheme should be shared with others using the project or workspace.


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The Manage Schemes dialog has four settings for each scheme plus several other controls, as shown in “The
manage schemes dialog.”
Figure 6-2

The manage schemes dialog

The four columns in the Manage Schemes dialog are used as follows:
Show

Displays or hides the scheme in the Scheme menu.

Scheme

Specifies the name of the scheme. You can edit this name.

Container

Specifies whether a scheme should be stored in a project—in which case it’s available in
every workspace that includes that project—or in the workspace—in which case it’s
available only in that workspace.

Shared

Specifies that the scheme is visible to anyone using that project or workspace (depending
on where the scheme is stored). Be sure to check with other people using the project or
workspace before deleting or modifying a shared scheme.

You can drag the schemes to reorder their appearance in the dialog and the Scheme menu.
The Add (+) button allows you to create a new scheme or duplicate the selected scheme. The Remove (–)
button allows you to delete the selected scheme. The Action menu allows you to export the selected scheme
or import an exported scheme.
The Edit button dismisses this dialog and displays the selected scheme in the scheme editor.
If the Autocreate schemes checkbox is selected, when you add a new target to your project, Xcode automatically
creates a scheme for it. If the checkbox is not checked, then you can click the Autocreate Schemes Now button
to have Xcode create new schemes for any targets that don’t have them.


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Configure and Execute Actions

There are five actions that you can perform with Xcode:
●

Run

●

Test

●

Profile

●

Analyze

●

Archive

Each of these actions requires you to first build your code. Exactly what is built is specified by the scheme you
choose and how that scheme is configured. In addition to the Build pane in the scheme editor, which specifies
which targets are built for each action, there is a configuration pane for each action.

Run Your Application to Debug It
Although a scheme can specify any number of targets to be built when you click the action button, Xcode can
launch and debug only one executable at a time. “The scheme editor Run pane” shows the Info pane for the
Run action.
Figure 6-3

The scheme editor Run pane


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You can specify whether to use a debug or release build configuration (or any other build configurations you
added) and which debugger to use.

Xcode Debuggers
Different debuggers provide different information and error messages. Xcode currently provides the GDB and
LLDB debuggers.

Debug vs. Release Builds
A debug build includes symbols that can be used by a debugger to display your source code when your
program stops at a breakpoint and to show you the values of your variables at that point. For a release build,
you normally want to strip that information out, because the debug information makes it very easy to
reverse-engineer the program. Release builds also typically do code optimization that isn’t done for debug
builds. Because the Run action is normally used for debugging, most developers use a debug build configuration
for the Run action. However, you might occasionally want to build and run your application with the release
configuration to see what size your application will be and to make sure there are no problems introduced by
the code optimization; that is, to make sure your application runs as you expect.

Arguments and Environment Variables
Other panes for the Run action let you provide arguments and environment variables to pass to your executable
on launch, and a number of diagnostic options, such as for memory management and logging.
Specify runtime arguments for your application when you run it in Xcode.

To run your application with arguments . . .
1.


2.


3.

In the left column, select Run.

4.

To specify runtime arguments, click Arguments.

5.

Click OK.


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6.

Click the Run button or choose Product > Run.

Schemes contain a Run action that affects what happens when you choose Product > Run. To specify
runtime arguments, click the Arguments tab. You can specify arguments passed on launch, environment
variables, and modules for which to load debug symbols.
During the test and debug phases of your product development, configure a scheme to run your application
with various memory management diagnostics and logging options enabled. Schemes have a Run action with
a Diagnostics pane that allows you to choose from a selection of runtime diagnostic tools.

To run your application with diagnostics . . .
1.


2.


3.

In the left column, select Run.

4.

To specify runtime diagnostics, click Diagnostics.


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5.

Click OK.

6.

Click the Run button or choose Product > Run.

Select the tools that you want Xcode to use. You can view output from these tools in the debug area console
and in the debug log in the log navigator.
Memory Management options:
●

Enable Scribble. Fill allocated memory with 0xAA and deallocated memory with 0x55.

●

Enable Guard Edges. Add guard pages before and after large allocations.

●

●

Enable Guard Malloc. Use libgmalloc to catch common memory problems such as buffer overruns
and use-after-free.
Enable Zombie Objects. Replace deallocated objects with a “zombie” object that traps any attempt
to use it. When you send a message to a zombie object, the runtime logs an error and crashes. You
can look at the backtrace to see the chain of calls that triggered the zombie detector.

Logging options:


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●

●

Distributed Objects. Enable logging for distributed objects (NSConnection, NSInvocation,
NSDistantObject, and NSConcretePortCoder).
Garbage Collection Activity. Enable various logging facilities in the garbage-collected memory allocator.
Log when a collection occurs, log when new regions are allocated, and log all weak reference
manipulations.

●

Malloc Stack. Record stack logs for memory allocations and deallocations.

●

Log Exceptions. Log Objective-C runtime exception handling.

●

Log DYLD API Usage. Log dynamic-linker API calls (for example, dlopen).

●

Log Library Loads. Log dynamic-linker library loads.

Debugger options:
●

Stop on Debugger() and DebugStr(). Enable Core Services routines that enter the debugger with a
message. These routines send a SIGINT signal to the current process.


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Location Simulation
In Xcode 4.2 and later, you can simulate locations other than your current location in iOS applications that use
Core Location. To set a location, choose Edit Scheme from the scheme selector in the toolbar, select the Run
action, and click the Options tab. You can then choose a location from the Location menu (“Choosing a location
in the scheme editor”). To set a location in the debug bar, see "Set a Location in the Debug Bar" (page 196).
Figure 6-4

Choosing a location in the scheme editor

Run Unit Tests to Find Regressions
Whenever you make changes to your code, there’s a chance that you’ve introduced bugs and that the code
will no longer run as expected. As a quality control measure, you can create programs, called unit tests , that
automatically exercise the features of your application and check the results. Each unit test is a separate bundle
containing code for a set of test cases, each of which exercises some subset of your application’s features. Test
cases are organized into test suites. In code, you create classes that are subclasses of the SenTestKit test
suite base class. Each such class in the bundle is a test suite, and any methods in those classes that begin with
the string test are the test cases.


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Choosing the Test action causes Xcode to build the targets you specified for the test action in the Build pane
of the scheme editor and then executes the test cases you enabled in the Test pane. Normally, you create one
or more test targets that are separate from your application product targets.
The Xcode development installation includes a framework for testing Objective-C code—the senTestingKit
framework—which provides methods you can use to exercise methods in your code and test the results.
For references and more reading on unit tests and the senTestingKit framework, see the Sen:te website.

To include unit tests when you create a new project
1.

Choose File > New > New Project and select the Include Unit Tests option in the Choose Options pane
of the New Project dialog.

2.

Select the Include Unit Tests option in the Choose Options pane of the New Project dialog.

The Include Unit Tests option is available for both Mac OS X and iOS projects. When you select this option,
Xcode provides your project with a test target and with header and implementation template files that use
the senTestingKit framework.
If you want to add unit tests to an existing project, you need to first add a target for the tests and then add
your source code to the target.


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To add unit tests to an existing project
1.

Select the project in the project navigator to open the project editor.

2.

Click the Add Target button at the bottom of the editor pane.

3.

In the Other category of templates, select a bundle template for your project:
●

For Mac OS X, select the Cocoa Unit Testing Bundle template.

●

For iOS, select the Cocoa Touch Unit Testing Bundle template.

4.

Click Next.

5.

Specify a name for the test set and click Next.

6.

In the confirmation dialog, make sure you’ve selected the correct project to which you’re adding the
target and click Save.

Note that you can select several or all of your class implementation files in the project navigator (use
Command-click for discontinuous selections) and set their target memberships all at once.
If you want to add additional test sets to your test target, you can drag an Objective-C test case class file from
the File Template library into your project navigator. Add the file to your test target, not to the application
target, as the file links correctly only if it’s in the test target. Note that dragging a test case class file from the
File Template library into your project does not add a test target to your project.


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Having created a test target with one or more test class template files, it’s time to write your unit tests and run
them.

To write and run your unit tests
1.

In the header file for your test class, import any headers from your project that declare methods that
your tests will exercise.

2.

Define your test methods in the test class implementation file.

3.

Add the source implementation files for any of your project’s classes exercised in your tests to your
test target by selecting the target’s checkbox in the Target Membership section of the File inspector.

4.

Select the scheme you want to use to run the tests in the Scheme pop-up menu and choose Edit Active
Scheme from that menu.

5.

Add your test target to the scheme by clicking the Add (+) button at the bottom of the Build pane of
the scheme editor.


166


6.

Make sure the Test checkbox for the test target is selected (as shown here).

7.

In the Test pane of the scheme editor, select each test you want to run.

8.

Choose Product > Test to run the tests.


167


9.

Read your tests’ console output in the Console pane of the debug area (or in the test log in the log
navigator).

Each test case is a method in your test class and can be individually selected or deselected in the Test pane
of the scheme editor. The Test action is enabled after you have at least one test case defined and selected.

Profile Your Application to Find Problems and Optimize Your Code
You can profile your application in order to find problems and optimize your code. Do so using the built-in
Instruments application. Instruments runs your executable, collecting and displaying data that you can use to
find problems such as memory leaks and unguarded file system access. It also helps you optimize aspects of
execution, such as CPU use, file activity, and the use of threads. There are also specialized instruments for
specific frameworks such as Core Data and OpenGL. Although you can run individual instruments, it’s common
to run sets of instruments together, such as several instruments that monitor overall system activity. The
Instruments application comes with a set of templates, each of which includes one or more instruments. You
can also define your own templates. For more information on the Instruments application and instruments
templates, see Instruments User Guide .
You use the scheme editor’s profile pane to specify which template Instruments should use when you choose
the Profile action.

To specify an Instruments template for the Profile action
1.

Open the scheme editor.


168


2.

Select the Profile pane.

3.

Choose an instrument template from the Instrument pop-up menu.
The default choice is Ask on Launch, which causes Instruments to display its template chooser dialog
when it starts up.

If you select a blank template from the Instruments template chooser, you can drag one or more individual
instruments into the Instruments window to be run with your application. You can save the set of instruments
as a custom template, in which case it becomes available as a choice in the Instrument pop-up menu of
the Profile pane.

Perform Static Analysis To Find Semantic Problems
The Analyze action performs a static analysis of your code. The only option for the Analyze action in the scheme
editor is whether to analyze a debug or release build. To specify which targets should be included in the
analysis, use the checkboxes in the Analyze column of the Build pane. Static analysis is discussed in "Locate
Possible Semantic Problems" (page 181).

Create an Archive for Sharing or Submitting Your Program
The Archive action creates an application bundle you can use to share your program with others or to submit
your application to the App Store. Because it’s unusual to share a debug version of an application, most
developers set the build configuration to Release in the Archive pane of the scheme editor. To distribute
frameworks, plug-ins, and other targets with your application, select the checkboxes for those targets under


169


the Archive column in the Build pane of the scheme editor. You probably don’t want to distribute unit tests
with your application, on the other hand, so you should not select the checkbox for the test target in the
Archive column.
For more information on the use of archives, see "Distribute Your App" (page 284).

Initiate an Action
You can initiate an action in several ways.

To initiate an action
●

Click and hold the action button at the left end of the toolbar, then choose the action you want from
the pop-up menu.

If you click this button without holding it, Xcode initiates the action currently displayed by the button.
●

Choose an action from the Product menu.

●

Use a keyboard shortcut.
There are keyboard shortcuts for every action except Archive (open the Product menu to see the list).
Tip: Hold down the Option key to see additional shortcuts.

The action button and each of the items at the top of the Product menu (Run, Test, Profile, Analyze, Archive)
cause the targets specified by the Build pane of the scheme to be built before performing the specified action.
Other items in the menu allow you to build without other actions, or to perform the other actions using the
last build without building again.


170


To open the scheme editor before initiating an action
1.

Hold the Option key when you choose the action.
The scheme editor opens to give you the opportunity to check or change the scheme settings before
you run the application.

The OK button at the bottom of the scheme editor is replaced with two buttons: the name of the action
(here, Profile) and Done.
2.

Click the action button in the scheme editor.
Any changes you made to the scheme are saved and the action is carried out using the new settings.
Tip: Click Done to save any new scheme settings and close the scheme editor without building
the application.


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Customize Your Build and Run Workflow

You can specify behaviors that affect your build and run workflow through the Xcode Behaviors preferences.
The Behaviors preferences pane lets you specify what should happen when a variety of events occur (“Behaviors
preferences”)—including, but not limited to, scheme actions.
Figure 6-5

Behaviors preferences

For example, you can have Xcode display the debug area when your code pauses at a breakpoint, or Xcode
can display the issue navigator when a build fails. If you are searching for text or a symbol name in a large
project, you can set preferences to let you know when the search has completed, either with or without results.
Tip: In addition to the Behaviors preferences setting to create a snapshot, you can specify that Xcode create a
snapshot before a mass editing operation such as a refactoring transformation. To do so, select the Snapshots
pane in the File > Project Settings or File > Workspace Settings dialog.

You can name a tab and specify that tab as the display to use when an event occurs. Then you can set up the
display in that tab exactly as you want it. If the tab doesn’t exist when the alert is triggered, Xcode creates the
tab for you, set up as it was when you created it. For example, in “Behaviors preferences,” Xcode is configured
to play a sound and open a tab named SketchDebug when the run pauses (such as when a breakpoint is


172


triggered). The tab will have the debug area and debug navigator open. If you configure the tab to include an
assistant editor and to display the debug area with the log pane closed, then every time a breakpoint is
triggered, a tab named SketchDebug opens with those characteristics.

To name a tab
●

To give a custom name to a tab, double-click the title of the tab and type the new name.
Tab names are case sensitive in the Show Tab field of the Behaviors preferences.

Xcode remembers the state of the named tab—including which window it was in—when it reopens the tab.
By naming a tab in a separate window, you can use the “Show tab” option in Behaviors preferences to
automatically open a new window.

To automatically open a new window
1.

Open and name a new tab.

2.

Drag the tab out of the workspace window to create a new window.

3.

Set up the new window exactly as you want it.

4.

In Behaviors preferences, select the event for which you want the new window to open.

5.

For that event, select the Show tab checkbox and type the name of the tab.

You can also can design custom behaviors that are triggered by menu items or their key equivalents.

To create a custom behavior
1.

In the Behaviors preferences pane, click the plus button at the bottom of the left column.


173


2.

type the name of the new behavior and press Return.

3.

Select checkboxes to specify what should happen when you invoke this behavior.

For example, you can create a "Unit Testing" behavior that creates a snapshot and runs your unit tests. After
you’ve created a behavior, it appears in the Xcode > Behaviors menu.
You can assign a key equivalent for each of your custom behaviors.


174


To assign a key equivalent to a custom behavior
1.

In the Key Bindings preferences pane, select the Customized tab to find the behavior for which you
want to assign a key equivalent.

2.

Click the Key column on the line of the behavior in order to open a text field.

3.

With the text field selected, press the keys you want to use for the key binding.

4.

Click outside the text field to complete the operation.
Note: If you don’t click outside the text field and instead press a key (such as Return), Xcode
enters the key you pressed into the text field.


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Fine-Tune Your Builds

Tip: If the key binding you specify conflicts with another, a red circle with an exclamation mark appears at
the right edge of the key column. Xcode does not save the new key binding until you resolve the conflict.
Click the Conflicts tab to see the other command or commands that use the same key combination.

Most developers can get by with the default build settings, except for the few that must be set—or at least
checked—for every project (see "Set the Basic Build Settings" (page 69)). You may have special needs, however,
that require anything from tweaking a setting or two to creating an entirely new build configuration. To check
or change build settings, click the project in the project navigator to open the project editor. Control-click in
the left column of the project editor where the projects and targets are listed to see a list of project editor help
topics (“Project editor help topics”).
Figure 6-6

Project editor help topics

You can edit build settings at the project or target levels. Most build settings have a system default. If you click
Levels in the build settings header bar, Xcode shows you the resolved value for each build setting and indicates
with green highlighting the level at which the value was set.
Customize aspects of your product’s build process by editing its build settings.


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To edit a build setting . . .
1.

In the project editor, select the project or target whose build setting you want to edit.

2.


3.

Locate the build setting in the left column.

4.

Set the value for the build setting in the right column.


You set build settings at either the project level or the target level. To see all the levels of build settings,
select Levels rather than Combined.
The lowest level at which a build setting is defined takes precedence. If you define a build setting at the
project level, the definition is set for the corresponding project, and it’s applied to all the targets that belong
to that project. If you define a build setting at the target level, the definition applies only to the corresponding
target.
Definitions applied at the target level override definitions set at the project level. The level at which the
build setting is defined is highlighted in green. For example, at the beginning of the video, the Architecture
build setting is highlighted in green at the default level. At the end of the video, after the setting has been
redefined at the target level, the Architecture build setting is highlighted in green at the target level.
If you have changed or customized a setting, it’s shown in boldface.
The video shows changing the compiler build setting for a target.
You can see documentation on a build setting in the Symbol inspector in the utility area.
Find concise documentation for a build setting using Quick Help.

To see documentation on a build setting . . .
1.


2.

Display the Symbols inspector.

3.

Select a build setting.


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4.

View the documentation under Quick Help in the Symbols inspector.


Quick Help provides a persistent location for build setting documentation without taking your focus away
from the build settings pane. Whenever you select a build setting, Quick Help displays information about
that item.
The video shows viewing information on a build setting in Sketch.
Alternative: Option—double-click a build setting to open Quick Help in a separate window.
Unlike Quick Help in the utility area, the Quick Help window is not persistent.

Control the Order in Which Xcode Builds Your Products
Xcode detects when one of your products is dependent on another and automatically builds them in the
correct order. However, in the unusual event that you need to control the order in which Xcode builds your
products, you can create explicit target dependencies by using the Build Phases pane of the project editor.
Ensure that targets are built in the proper order using target dependencies. In a complex project, you may
have several targets that create related products. Frequently, these targets need to be built in a specific order.

To ensure products are built in the correct order . . .
1.

In the project editor, select the target to which you want to add a dependency.

2.

Click Build Phases at the top of the project editor.

3.

Open the Target Dependencies section.

4.

Click the Add (+) button to add a target dependency.


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5.

Select a target from the list and click Add.


For example, a project for a client-server software package may contain targets that create a client application,
a server application, tools that provide command-line interfaces to the client and server, and a private
framework that all the other targets use. For the project to build correctly, the private framework needs to
be built before the other targets—that is, the other targets have a dependency on the private framework.
The video illustrates adding a private framework to the client application target’s dependency list.
The Build Phases pane of the project editor also lets you specify the order in which files are compiled and
linked, specify which bundle resources are copied and in what order, and so forth. You can drag the build
phases into a different sequence if you wish, and you can drag the individual files in each build phase into
whatever order you want. Doing so is advisable only if you have a good reason to do so and know exactly what
you’re doing.


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Xcode provides all the facilities you need to analyze and debug your code in the workspace window. This
chapter summarizes those facilities.

Select a Debugger
Xcode comes with GDB and LLDB debuggers, with GDB selected by default.
LLDB is a debugger that is part of the LLVM open source compiler project (see the LLVM home page at
http://llvm.org/). With few exceptions, the user interfaces for debugging are identical for the two debuggers.

To change the debugger
1.

From the Scheme pop-up menu, choose Edit Active Scheme.

2.

In the leftmost column of the scheme editor, select the Run action.

3.

In the Info pane, choose the debugger you want to use from the Debugger pop-up menu.


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Find Coding Mistakes

At any time in your code development, you can run the static analyzer to find potential semantic problems in
your code. In addition, when you build your project, the compiler returns messages, warnings and errors that
you can use to find and correct mistakes in your code.
Note that if you use the LLVM compiler, Fix-it scans your code and flags possible errors as you type ("Have
Fix-it Flag Errors as You Type" (page 129)).

Locate Possible Semantic Problems
Use static analysis to examine the semantics of your code to find potential problems with your program logic.
Xcode lets you perform the analysis, examine the results, and edit your source files all within the workspace
window.
You run the static analyzer by selecting the project you want to analyze in the project navigator and then
choosing Analyze from the Product menu. You can use the Build pane of the scheme editor to specify which
targets are included in the analysis.
Tip: If you want to open the scheme editor to set options before running the static analyzer, hold the Option
key while choosing Product > Analyze.

Find flaws—potential bugs—in the source code of a project with the static analyzer built into Xcode. Source
code may have subtle errors that slip by the compiler and manifest themselves only at runtime, when they
could be difficult to identify and fix.

To perform static code analysis . . .
1.

Choose Product > Analyze.

2.

Select an analyzer message in the issue navigator.

3.

Click the corresponding message in the source editor.

4.

Use the pop-up menu in the analysis results bar above the edit area to study the flow path of the flaw.

5.

Edit the code to fix the flaw.



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The Xcode static analyzer parses the project source code and identifies these types of problems:
●

Logic flaws, such as accessing uninitialized variables and dereferencing null pointers

●

Memory management flaws, such as leaking allocated memory

●

Dead store (unused variable) flaws

●

API-usage flaws that result from not following the policies required by the frameworks and libraries
the project is using

You can suppress false positive messages from the analyzer using assertions, attributes, or pragma directives.
When you analyze a project for the first time, you may uncover a lot of issues. But if you run the static
analyzer regularly and fix the flaws it uncovers, you should see fewer problems in subsequent analyses.
Analyze early; analyze often. It’s good for the code.
Note that if the static analyzer reports no problems, you can't assume that there are none. The tool cannot
necessarily detect all the flaws in the source code.
The video shows the process of looking at a flaw in the source file SKTText.m.


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Tip: Choose Product > Clean to remove the analyzer messages from the issue navigator.

Locate and Display Build Issues
You can build and run the executable specified by the active scheme by clicking the action button at the left
end of the toolbar. Other options, such as running without building or building without running, are available
in the Product menu.
Figure 7-1

The issue navigator

If the compiler finds any problems while building, the issue navigator opens. You can display problems by file
or by type (Figure 7-1). Filters at the bottom of the navigator let you display only issues from the latest build,
only issues associated with the current scheme, only errors (suppressing any warnings), or only issues that
include text matching a string you enter in the filter field.

To navigate through build issues
●

Use the issue pop-up menu at the right end of the jump bar.


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The issue menu appears as a yellow triangle if the most serious issue listed is a warning (
red octagon if any errors are listed (
through the errors.

●

) or as a

). Choose an error from the menu or use the arrows to cycle

Select any of the errors or warnings in the issue navigator to display in the source editor the line of
code where the problem was discovered.

Click the number at the right margin of an issue to see a list of all the issues associated with the line
of code.


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To view build issues with the log navigator
1.

Select a build in the build log.
The build results are displayed in the editor area.

2.

Open an assistant editor and set it to Referenced Files.

3.

Select an issue in the log to see it displayed in the assistant editor.


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4.

Double-click an issue in the log to see it displayed in a separate window or tab (depending on the
double-click setting in the General pane of Xcode Preferences).

Whereas the issue navigator is the common place to go to see build errors and warnings, build logs are where
you can see details about what happened during a build. For example, if you want to make sure files were
built in the right order, ensure that a particular file got rebuilt, or track down some advanced project
configuration problem, you can get the information you need in the build log.

To view build result details
●

●

Click the list icon (
and results.

) at the end of a build command line in the build log to see the full build command

Option-click a build issue to open the full build results to that issue.
The issue highlights briefly when the full build results open.


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As of Xcode 4.1, you can select what kind of content to view when debugging: source only (when available),
disassembly only, or source and disassembly. The disassembly is the set of assembly-language instructions
seen by the debugger while your program is running. Viewing the disassembly can give you more insight into
what your code is doing when it’s stopped at a breakpoint. By viewing the disassembly and source code
together, you can more easily relate the instruction being executed with the code you wrote.

To view disassembly while debugging
●

Choose Product > Debug Workflow > Show Disassembly When Debugging.
The disassembly is displayed in the editor pane.

●

Open an assistant editor and choose Disassembly from the Assistant pop-up menu in the assistant
editor jump bar.
The source and disassembly are shown in the split editor pane.


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Manage Breakpoints

Manage Breakpoints
Although you can use the debugger to pause execution of your program at any time and view the state of the
running code, it's usually helpful to set breakpoints before running your executable so that you can stop at
known points and view the values of variables in your source code.

Add and Activate Breakpoints
To set breakpoints, open a source-code file and click in the gutter next to the spot where you want execution
to stop. When you add a breakpoint to the code, Xcode automatically activates breakpoints, as indicated by
inactive:
). You can toggle the state of breakpoints
the breakpoint-state button in the toolbar (active:
at any time by clicking the breakpoint-state button. You can also disable an individual breakpoint by clicking
its icon. To remove a breakpoint completely, drag it out of the gutter.
You can set several options for each breakpoint, such as a condition, the number of times to pass the breakpoint
before it’s triggered, or an action to perform when the breakpoint is triggered.

To set breakpoint actions and options . . .
1.

In the breakpoint navigator, Control-click the breakpoint, and choose Edit Breakpoint from the shortcut
menu.

2.

Set the actions and the options for the breakpoint in the breakpoint editor.

Specify what Xcode does when a breakpoint is triggered with the breakpoint editor.
Each breakpoint type has specific properties that define it, such as condition and ignore count (for file line
breakpoints), symbol name (for symbolic breakpoints), and exception type (for exception breakpoints). But
all breakpoint types share two properties:
●

Action: Specifies what actions Xcode performs when the breakpoint is triggered. You can have Xcode
execute an AppleScript script or a shell or debugger command, log or speak a message, or emit a
sound.


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Manage Breakpoints

●

Options: Specifies additional breakpoint behavior, such as whether to continue program execution
after performing actions.

The screenshot shows a file line breakpoint that is ignored the first five times it is hit. Subsequent hits trigger
the breakpoint, which causes Xcode to emit a sound and continue program execution.
In addition to conditional breakpoints, which are triggered when a specific condition is met, you can create
breakpoints that are triggered when a specific type of exception is thrown or caught, and symbolic breakpoints,
which are triggered when a specific method or function begins execution.
Add an exception breakpoint to your project in the breakpoint navigator.

To add an exception breakpoint . . .
1.

In the bottom-left corner of the breakpoints navigator, click the Add button.

2.

Choose Add Exception Breakpoint.

3.

Choose the type of exception from the Exception pop-up menu.

4.

Choose the phase of the exception handling process at which you want program execution to stop.

5.

Click Done.

The Exception pop-up menu specifies the type of exceptions on which you want execution to stop:
●

All. Stops on all exceptions.

●

Objective-C. Stops on Objective-C exceptions.

●

C++. Stops on C++ exceptions.
To stop on a particular C++ exception, specify the exception name.

The screenshot shows the properties of an exception breakpoint.

To add a symbolic breakpoint . . .
1.

In the bottom-left corner of the breakpoint navigator, click the Add button.


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Debug Your App
Manage Breakpoints

2.

Choose Add Symbolic Breakpoint.

3.

Enter the symbol name in the Symbol field.

4.

Click Done.

Add a symbolic breakpoint to your project in the breakpoint navigator. Symbolic breakpoints stop program
execution when a specific function or method starts executing.
You can specify the symbol as:
●

●

●

A method name. For example, pathsMatchingExtensions:.
A method of a particular class. For example, [SKTLine drawHandlesInView],
people::Person::name().
A function name. For example, _objc_msgForward.

If the symbol is declared in more than one library, enter the name of the appropriate library in the Module
field.
The screenshot shows the properties of a symbolic breakpoint.

Edit Breakpoints
For existing breakpoints, you can edit options or change their scope—that is, the project or workspace in which
the breakpoint appears.

To edit breakpoint options
1.

Open the breakpoint navigator and Control-click the breakpoint whose options you want to edit.

2.

From the shortcut menu, choose Edit Breakpoint.


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Debug Your App
Manage Breakpoints

3.

In the Condition field of the options dialog, specify an execute condition for the breakpoint (if any).

The breakpoint is triggered only if the condition is true (for example, i == 24). You can use any variables
that are in the current scope for that breakpoint.
You must cast an function calls to the appropriate return type.
4.

Specify values for any other actions you want to set and click Done.

By default, a new breakpoint is local to the workspace you have open. If you add the project containing that
breakpoint to another workspace, the breakpoint is not copied to the new workspace. You can assign breakpoints
to other scopes, however. If you move a breakpoint to User scope, it appears in all of your projects and
workspaces. If you move a breakpoint to a specific project, then you see this breakpoint whenever you open
that project, regardless of which workspace the project is in.

To change the scope of a breakpoint
1.

In the breakpoint navigator, select the breakpoint or breakpoints you want to assign to a new scope.

2.

Control-click one of the breakpoints, and from the shortcut menu, choose Move Breakpoints To.


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Debug Your App
Manage Breakpoints

3.

If you have a workspace window open, your choices include Workspace, User, and all of the projects
in the workspace:

If you have a project open without a workspace, your choices are User and the project you have open:

4.

Choose Workspace to have the breakpoint appear only in this workspace. Choose User to have the
breakpoint appear in all your workspaces and bare projects. Choose a specific project to have the
breakpoint appear whenever that project is open, regardless of which workspace it’s in.

5.

Your choice is reflected in the organization of the breakpoint navigator.

Share Breakpoints
You can share any breakpoints with other users.


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Manage Breakpoints

To share breakpoints
1.

In the breakpoint navigator, select the breakpoint or breakpoints you want to share.

2.

Control-click one of the breakpoints, and from the shortcut menu, choose Share Breakpoints.

3.

Xcode moves the shared breakpoints into their own category in the breakpoint navigator:

A breakpoint with User scope cannot be shared. If you select a User breakpoint and choose Share Breakpoint
from the shortcut menu, Xcode moves the breakpoint to the local (Workspace or individual project) category
and shares it.

Set Preferences for Breakpoint Behavior
The “Run pauses” option in Behaviors preferences specifies what Xcode does when a breakpoint is triggered
and the running application pauses. By default, Xcode opens the debug navigator and debug area, showing
the location of the breakpoint in your code and the status of the application’s threads and stacks. However,
you can customize this behavior, specifying various sorts of behaviors (such as a sound or announcement),
which navigator to open, and whether to navigate to the first new issue. You can even design a tab with the
layout you prefer, name the tab, and have Xcode re-create it when a breakpoint is triggered. For more
information on Behaviors preferences, see "Customize Your Build and Run Workflow" (page ?).


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Debug Your App
Customize the Debug Area

Customize the Debug Area
If you pause execution or a breakpoint is triggered, the debug area opens, displaying the values of variables
and registers plus the debug console (Figure 7-2). You can use the buttons at the right end of the debug area
toolbar to display both the variables and console panes or to hide either one.
Figure 7-2

The debug area

The Variables Pane
The variables pane displays variables and registers. You specify which items to display using the pop-up menu
in the top-left corner of the variables pane:

●

Auto displays only the variables you’re most likely to be interested in, given the current context.

●

Local displays local variables.

●

All displays all variables and registers.


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Debug Your App
Control Program Execution

Use the search field to filter the items displayed in the variables pane.

The Console Pane
The console pane displays program output and lets you enter commands to the debugger tool. You specify
the type of output the console displays with the pop-up menu in the top-left corner of the console pane:
●

All Output displays target and debugger output.

●

Debugger Output displays debugger output only.

●

Target Output displays target output only.

When you execute a program from Xcode, the debug bar appears at the bottom of the editor pane. You can
use the debug bar to control program execution and to navigate through threads and stacks. You can also
step through code and control execution in the source editor and you can suspend a thread in your running
application.
To make it easier to debug full-screen applications, you can set Xcode to a window-in-front mode that lets you
control program execution without obscuring your program window.

Step Through Code with the Debug Bar
The debug bar includes buttons to:
●

Open or close the debug area

●

Pause or resume execution of your code

●

●

●

Step over; that is, execute the current line of code and if it is a routine) return to the next line in the current
file
Step in; that is, execute the current line of code and (if it is a routine) jump to its first line
Step out of a jumped-to routine; that is, complete the current routine and step to the next routine or back
to the calling routine

Control-click to step through your code by assembly language instruction instead of by statement. The step
icons change to show a dot rather than a line under the arrow.
Control-Shift-click to perform the action in the active thread while holding other threads stopped. The step
icons show a dashed rather than solid line under the arrow.


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Tip: To see which key combination performs which action, look in the Product > Debug menu while a debugging
session is in process.

Set a Location in the Debug Bar
if you are running an application for iOS 5.0 or later that uses Core Location, the debug bar has a location
drop-down menu (Figure 7-3). To set a location in the Run action of the scheme editor, see "Location
Simulation" (page ?).
Figure 7-3

Choosing a location in the debug bar

Step Through Code in the Source Editor
While your code is paused at a breakpoint or because you clicked the pause button, you can continue execution
or step through your code in the source editor.
To continue execution to a specific line of code, hold the pointer over the gutter next to the target code line
until the continue-to-here icon appears, then click the icon.


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To step to the next instruction, hold the pointer over the gutter next to the instruction pointer until the step-over
icon appears, then click the icon.

Suspend a Thread
Suspend a thread to prevent it from running during your debugging session. You might suspend a thread if
the thread is about to crash or if you want to prevent it from doing work that could interfere with the rest of
your application.

To suspend a thread in your running application . . .
1.

Pause your application’s execution, or wait for it to hit a breakpoint.

2.

In the Debug navigator, Control-click the desired thread.


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3.

In the contextual menu, choose Suspend Thread.

A suspended thread does not run when you step through your code or continue execution. The debug
navigator places a red status icon next to suspended threads.
To resume a thread that is currently suspended, Control-click it and select Resume Thread from the contextual
menu.
The screenshot shows the Suspend Thread command in the contextual menu of the debug navigator.


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Important: Although suspending threads can help you debug your application, it can also have other
consequences. For example, suspending a thread that holds a lock could cause other threads to deadlock.

Set Xcode Window Behavior
When you run your application from Xcode in order to debug it, you have both Xcode and your application
open on your monitor. In some cases—for example, when you have a full-screen application and only one
monitor—you might want to keep Xcode behind your application and use keyboard shortcuts to control
window execution. Choose Product > Window Behavior > Xcode Behind to keep Xcode behind your application.
If you need to be able to see the debug area and other debugging information when you stop your application
or it pauses at a breakpoint, however, you can instead choose Product > Window Behavior > Xcode In Front
to keep Xcode in front of your application. In this case, while your application is running, the Xcode application
shrinks to a minimum size, displaying a minimum set of controls. In Figure 7-4, the Xcode window is indicated
with a red box.
Figure 7-4

Xcode In Front window mode while the executable is running

Click the Console button to open the debug console while the application is running. Click the Focus button
to allow the focus to switch between the application and Xcode.


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Examine Threads, Stacks, Variables, and Memory

When you pause execution or your program hits a breakpoint, Xcode expands to show the debug pane (Figure
7-5). When you continue execution, Xcode shrinks again.
Figure 7-5

Xcode In Front window mode while the executable is paused

When you pause execution of your code (see "Control Program Execution" (page 195)) or the running code
triggers a breakpoint, Xcode opens the debug navigator, displaying the threads that were running when
execution paused. Under each thread is the stack at that point in program execution. You can examine the
threads and stacks in the debug navigator, using the filters at the bottom of the navigator to control the scope
of threads and stacks so you can concentrate on the level of detail that is most useful to you. You can also
navigate through threads and stacks in the debug bar of the debug area.
You can view variable values in the debug area or source editor, and you can use the debug area and editor
pane together to view the contents of memory locations.

To view threads and stacks in the debug navigator
1.

Set breakpoints at the locations where you want to examine threads and stacks.

2.

Choose Run from the Product menu (or click the Run button).

3.

When execution pauses, select a stack frame in the debug navigator.
The corresponding source file or disassembled object code is shown in the source editor.


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Debug Your App

The slider at the bottom of the debug navigator controls how much stack information the threads and
stacks navigator displays. At the left end of the slider, the debug navigator shows only the top frame
of each stack. At the right end, it shows all stack frames. Click the button at the left end of the slider (
) to toggle between displaying all the active threads or only threads that have your code in them (as
opposed to system library code). The figure shows the debug navigator when execution has stopped
at a breakpoint.

To view threads and stacks in the debug area . . .
1.

With the debug area open, run your application.

2.

Pause your application’s execution, or wait for your code to stop at a breakpoint.

3.

Choose a thread from the pop-up menu in the debug bar.

4.

Examine the corresponding source or assembly code.


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The debug area lets you examine the threads and stacks of a program being debugged. When you select
a thread or a stack within a thread in the debug bar, Xcode displays the corresponding source file or assembly
code in the main editor.
The screenshot shows the debug area while choosing a thread and a stack frame to examine.
Alternative: You can also view threads in the debug navigator.

Filter threads and symbols to remove extraneous information and focus on your own code during a debugging
session. The debug navigator sports two controls for filtering extraneous threads and program symbols: the
thread filter and the call stack slider.

To filter threads and symbols in the debug navigator . . .
1.

Pause your application’s execution or wait for your code to stop at a breakpoint.

2.

Use the thread filter button to hide threads that are not relevant to debugging.


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Debug Your App

3.

Use the call stack slider to adjust the amount of detail shown for each thread.

The thread filter button shows or hides threads that may not be relevant to debugging your code right
now. Examples of such threads include the heartbeat and dispatch management threads and any threads
that are idle and not currently executing any specific application code. Hiding these threads allows you to
focus on the threads that are doing actual work for your application.


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For each thread, the call stack slider dynamically collapses or expands the list of symbols displayed by that
thread. Collapsing the list helps you focus your debugging efforts by hiding calls that are far removed from
your code. (The presence of hidden symbols is indicated by a dotted line in the stack frame.) Expanding
the list lets you see the precise set of calls that occurred to reach the current stopping point.
The screenshots show the debug navigator in two states. The screenshot on the left shows the debug
navigator with the thread filter turned off and the call stack slider set to show all stack frames. The screenshot
on the right shows it with the thread filter turned on and the call stack slider set to show only the most
relevant stack frames.
Note: Filtering applies only to threads and their contents and does not apply to viewed memory
locations.

To view memory locations . . .
1.

In the debug area, Control-click the variable whose memory you want to view.

2.

Choose View Memory of “variable ” from the shortcut menu.


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3.

Use the debug navigator to select from among the viewed memory locations.

View memory locations to examine the raw contents of program variables. When you view a new memory
location from the debug area, an entry is added to the debug navigator and selected. The contents of the
selected memory entry are then displayed in the memory browser in editor pane.
The bottom of the memory browser contains controls you use to navigate the memory and customize its
display:
●

Address. Specifies the beginning address of the memory displayed in the memory browser.

●

Memory Page. Moves back or forward a memory page.

●

Number of Bytes. Specifies the number bytes in a memory page.

●

Byte Grouping. Specifies the size of the memory chunks displayed.

Memory locations are valid only while the application is running in the current debugging session. When
you quit the application, Xcode removes all memory entries from the debug navigator and discards them.
To remove a memory entry while you are still debugging, select the entry and press Delete.


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Debug Your App
Capture OpenGL ES Frames

Inspect the value of a variable in a datatip to uncover a problem in the source code.

To view variable values in the source editor . . .
1.

Place a breakpoint in the method you want to investigate.

2.

Run the project.

3.

When execution stops, place the pointer on a variable that comes before the breakpoint.

4.

In the datatip that appears, inspect the current value of the variable.


You can also view the values of variables in the variables pane of the debug area.
The video illustrates inspecting the value of an integer variable in the method windowDidLoad.

The debugging features for iOS OpenGL ES applications includes a facility for capturing and analyzing frames.
When frame capture is enabled in the scheme for the application, the debug bar provides a control for entering
the OpenGL ES frame debugging view.


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To enable this feature, you must run the application on a device and the device must be running iOS 5.0 or
later. Set the destination in the scheme menu to an iOS device and choose Edit Scheme from the scheme
selector in the toolbar. Select the Run action, click the Options tab, and select the OpenGL ES Enable Frame
Capture checkbox (Figure 7-6).
Figure 7-6

Enabling OpenGL ES frame debugging


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Debug Your App

When you build and run your OpenGL ES application, the debug bar includes a frame capture button (Figure
7-7). Click that button to capture a frame.
Figure 7-7

Frame capture button

You can use OpenGL frame capture to:
●

Inspect OpenGL ES state information.

●

Introspect OpenGL ES objects such as view textures and shaders.

●

Step through draw calls and watch the changes with each call.

●

Step through the state calls that precede each draw call to see exactly how the image is constructed.


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Debug Your App

Figure 7-8 shows a captured frame. The debug navigator has a list of every draw call and state call associated
with that frame. The buffers associated with the frame are shown in the editor pane, and the state information
is shown in the debug pane.
Figure 7-8

OpenGL ES frame capture


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Debug Your App

You can step through draw calls in the debug navigator, or by using the double arrows and slider in the debug
bar (Figure 7-9).
Figure 7-9

Controls for stepping through draw calls


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Debug Your App

When you use the draw call arrows or slider, you can have Xcode select the stepped-to draw call in the debug
navigator. To do so, Control-click below the captured frame and choose Reveal in Debug Navigator from the
shortcut menu (Figure 7-10).
Figure 7-10

Shortcut menu


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Debug Your App

You can also use the shortcut menu to toggle between a standard view of the drawing and a wireframe view
(Figure 7-11). The wireframe view highlights the element being drawn by the selected draw call.
Figure 7-11

Wireframe view


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Debug Your App

Open the Assistant editor to see the objects associated with the captured frame. In the Assistant editor you
can choose to see all the objects, only bound objects, or the stack. Open a second Assistant editor pane to see
both the objects and the stack for the frame at the same time (Figure 7-12).
Figure 7-12

Frame capture with two Assistant panes


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Debug Your App

Double-click an object in the Assistant editor to see details about that object. For example, if you double-click
a texture object, you can see the texture in detail. Figure 7-13 shows the data in a vertex array (VAO) object.
Figure 7-13

Vertex Array Object detail


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Make Projectwide Changes

Xcode enables you to replace text strings throughout your project and to perform refactoring operations. A
refactoring operation—such as creating accessor methods for a symbol or creating a superclass from a
class—changes code without changing its behavior.

Replace Text Strings
You can use the search navigator to replace text strings throughout your project or workspace (Figure 8-1).
(To make syntax-aware changes to symbol names, including within nib files, use the Rename refactoring
operation instead.)
Figure 8-1

Search and replace using the search navigator

The search and replace operation can be customized—for example, to limit the scope of the search or to match
the case of letters in the string—and provides a preview that you can use to accept or reject individual
replacements.


215


Note: The first time you perform a mass-editing operation such as search and replace, Xcode displays
a dialog giving you the option of first enabling automatic snapshots. You can change this setting
any time in the Snapshots pane of the File > Project Settings or File > Workspace Settings dialog.
You can use a snapshot to back out all of your changes at once if necessary.
If you don't have automatic snapshots enabled, you can make a manual snapshot of your project
before performing the operation by choosing File > Create Snapshot.

Replace All Instances of a Text String
The Replace command does pattern matching in text files and replaces instances of the search string with the
replacement text you specify.

To find and replace text in your project
1.

Click the Find pop-up menu in the search navigator and choose Replace.

2.

Type the text you want to find in the top text field and press Return.


216


Note: Xcode does not search for the text until you press Return while the cursor is in the search
field. The Preview and Replace buttons are not active until after you’ve performed the search
and one or more results are returned.

The Activity viewer in the workspace toolbar indicates when the find operation is in progress.

3.

Type the replacement text in the lower text field.

4.

Click Replace All to replace every occurrence of the Find text with the Replace text. To replace a single
result, click that result to select it and click Replace. To replace a subset of the occurrences found, use
Shift-click or Command-click to make your selection and click Replace.


217


To see a preview of the changes before proceeding, follow the procedure in "Replace Selected Instances
of a Text String" (page 218).

Replace Selected Instances of a Text String
See what your changes will look like in your source code before deciding which occurrences to replace by
using the search navigator’s preview feature.

To preview changes before replacing text
1.

Click the Preview button below the Replace text field.
The preview dialog appears, showing the current version of each potential replacement in the right
column and the new version in the left column. Each arrow points at the version being used. All the
potential replacements are selected by default.

2.

To change the status (from selected to deselected, or vice versa) of one or more replacements, do one
of the following:
●

●

Click the checkbox for that change in the left pane of the dialog. Click the checkbox next to a
filename to change all the items in that file.
Click the button in the center of the right pane for each item whose status you want to change.


218


●

3.

Use Shift-click or Command-click to select items in the list in the left pane, then press the Space
bar to change their status.

Click Replace to carry out the replacement of the selected items.

Customize the Search
The search navigator provides Find options to customize a search. For example, you can specify its scope and
whether the search should be case sensitive.

To specify a new scope for a search
1.

In the search navigator, click the magnifying glass in the search field to open the Find options.

2.

Open the “Find in” pop-up menu.
The default scope is the workspace. If you have more than one project in the workspace, your projects
are listed.

3.

Choose Custom to create your own custom scopes.


219


4.

In the Find Scopes dialog, click the Add (+) button to add a new custom scope.

5.

Use the pop-up menus to specify the scope.
Depending on your choices, you might also have to fill in or select a value for a third scope parameter.

6.

Select the name of the scope and type a new name for the scope to appear in the “Find in” menu.
You can reopen this dialog and change the name at any time.

7.

Repeat this procedure as many times as necessary to define all the custom scopes you want to use.
Click Done when you’re finished.


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Improve Your Code’s Structure Through Refactoring

8.

To see your custom scopes, open the “Find in” pop-up menu.

A refactoring operation improves the structure of source code without changing its behavior. You refactor to
make the code easier to maintain, or as a first step in making further changes to the code.
Note: Refactoring works only with C and Objective-C files.

Select the Source Code to Refactor
Before you can choose a refactoring operation (also called a transformation ) from the Refactor submenu in
the Edit menu or from the shortcut menu in the source editor, you have to select the symbol or source code
that you want to refactor. Only the refactoring operations appropriate for the selected text are available in the
menu. The descriptions of the refactoring operations at the end of this chapter specify what code to select for
each type of refactoring operation.
When you select the code and the refactoring operation, Xcode presents a dialog to let you select options and
specify symbol names where necessary.


221


Preview the Changes Before Executing the Operation
You have the opportunity to preview the changes and decide which files to include before applying the changes
by using the refactor preview dialog (Figure 8-2).
Figure 8-2

The refactor preview dialog

Deselect a file in the leftmost pane of the preview dialog to leave it out of the refactoring operation.
You can edit your source code directly in the preview dialog. Any such edits are shown in the preview and
included in the refactoring operation.
Before you’ve saved your updated files, you can use the Undo command in the Edit menu on a per-file basis
to back out changes.
Important: By default, your changes are saved automatically when you close or build the project. To change
this behavior, open the General pane of Xcode preferences and set the Auto-save option to Ask or Never
Save.

Run Unit Tests Before and After Refactoring
As part of your refactoring workflow, you should develop unit tests for code you plan to refactor. Run these
tests before and after a refactoring to verify that the refactoring operation doesn’t change the behavior of the
modified code. For more information on unit tests, see "Run Unit Tests to Find Regressions" (page ?).


222

Choose a Refactoring Operation

The refactoring operations provided by Xcode include renaming a symbol, extracting a function or method
from other code, encapsulating accessors for a symbol, creating a superclass of a class, moving an item up into
a superclass, and moving an item down into one or more subclasses.
The Rename refactoring operation changes the name of the selected item throughout your project files.

To change the name of an item throughout your project
●

Select any symbol except the declaration of a method inside a protocol interface, and choose Rename
from the Refactor submenu in the Edit menu (or from the shortcut menu in the source editor). (You
can rename such a method if the selection is a definition of such a method in a class that adopts the
protocol. That is, if the container of the selection is a protocol, you cannot rename it; if the container
of the selection is a class, you can.)
The Rename refactoring operation differs from the Find and Replace command in that Rename is
symbol- and context-aware. Find only matches strings. Rename is particularly useful with properties.
If you’re renaming a class and you have files that use that class in the filename, select the “Rename
related files” option to rename the files as part of the refactoring operation.

The Extract refactoring operation creates a function or method from selected code.

To extract a function or method
1.

Select code or code and comments within a function or method implementation, and choose Extract
from the Refactor submenu in the Edit menu (or from the shortcut menu in the source editor).
Xcode analyzes the context of the selected code and the variables it uses to determine the generated
routine’s parameters and return value.

2.

In the dialog that appears, name the new routine and its parameters, and select whether it is a method
or function.

The Encapsulate refactoring operation creates accessors (“get” and “set” methods) for a symbol and changes
code that directly accesses the item to use the accessor methods instead.

To create accessors for a symbol
●

Select a symbol that is an instance variable (ivar) or a member of a structure, and choose Encapsulate
from the Refactor submenu in the Edit menu (or from the shortcut menu in the source editor).

The Create Superclass refactoring operation creates a superclass from a class.


223


To create a superclass
1.

Select a symbol that is a class defined in your project, and choose Create Superclass from the Refactor
submenu in the Edit menu (or from the shortcut menu in the source editor).
The Create Superclass refactoring operation creates skeletal interface and implementation statements
for a superclass placed in the inheritance hierarchy between the selected class and its existing superclass.

2.

In the dialog that appears, name the new superclass and select whether to create new header and
implementation files for its interface and implementation statements or put them in the existing file.

The Move Up refactoring operation moves the declaration and definition of an item into the superclass of the
class where they currently reside, removing them from their former location.

To move the declaration and definition of an item into a superclass
1.

Select a symbol that is a method or instance variable in a class, not a category, where the class and
superclass are defined in your project, and choose Move Up from the Refactor submenu in the Edit
menu (or from the shortcut menu in the source editor).

2.

In the dialog that appears, select whether also to move methods that directly access the refactoring
item and that are defined in the same class as the refactoring item.

The Move Down refactoring operation moves the declaration and definition of the refactoring item to one or
more of the subclasses of the class that declares and defines the item.

To move the declaration and definition of an item into one or more subclasses
1.

Select a symbol that is an instance variable in a class, not a category, where the class is defined in your
project and one or more subclasses already exist, and choose Move Down from the Refactor submenu
in the Edit menu (or from the shortcut menu in the source editor).
The Move Down refactoring operation moves the declaration and definition of the selected variable
into a subclass of the class where it currently resides, removing it from its former location.

2.

In the dialog that appears, specify the subclass into which to move the variable declaration and
definition.


224

Manage Your Devices

You manage iOS devices in Xcode using the Devices pane of the Organizer window (Figure 9-1).
Figure 9-1

Devices organizer

Although you can do much of your debugging and testing of an iOS application using iOS Simulator, simulation
cannot completely match the results of running your application on the target devices; you must test your
application on actual devices to ensure that it runs as intended and to tune it for performance on actual
hardware.


225

Manage Your Devices
Set Up Your Device

Note: Before you can run your application on a device, you must first become a member of the iOS
Developer Program. See http://developer.apple.com/programs/ios to learn how to become a member.

Set Up Your Device
To use a device with Xcode, you must provide the device with a provisioning profile and install iOS on the
device.

Provision a Device
If you are a team administrator, or if your team administrator has already configured the necessary credentials
for you and your device, you can use the devices organizer to automatically download and apply the provisioning
profile.
Provision your iOS device to run generic apps on your device, such as sample apps.

To provision a device automatically for development . . .
1.

Open the Devices organizer.

2.

Connect your device to your Mac.


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Manage Your Devices
Set Up Your Device

3.

Select the device, and click “Use for Development.”

Developing apps requires a provisioned device. The provisioning process sets up the required certificates
and configuration data that Xcode needs to install your apps on your device. When you provision a device
for generic development, Xcode adds your device to the generic team provisioning profile. This provisioning
profile allows development of most (but not all) types of apps. For some types of apps (such as those that
use push notifications or in-app purchases), you must use a manually configured provisioning profile.
Some types of applications require manual provisioning. In such cases, your team administrator must first
configure the necessary credentials for you, using the iOS Provisioning Portal. Follow your administrator’s
instructions to download the appropriate provisioning profile, and then use the devices organizer to locate
the provisioning profile on your file system and apply it.
Provision your device manually when you develop an app that requires a specialized provisioning profile.


227

Manage Your Devices
Set Up Your Device

To provision a device manually for development . . .
1.

In the Devices organizer, select Provisioning Profiles in the Library section.

2.

Click Refresh.

3.

Identify the specialized provisioning profile you need to use.

4.

Drag the provisioning profile to the Provisioning Profiles group of the target device.

Apps that support push notifications or in-app purchases cannot use the generic team provisioning profile.
Instead, those types of apps must use a specialized provisioning profile, which you create in the iOS
Provisioning Portal.


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Manage Your Devices
Set Up Your Device

Important: Before you can install a specialized provisioning profile on your device, that provisioning
profile must:
●
Include your development certificate
●

Identify your device

Note: All of the credentialing and provisioning procedures can be performed using the iOS
Provisioning Portal, a restricted-access area of the iOS Dev Center that stores information about your
development devices. For details, see Tools Workflow Guide for iOS .

Restore or Install a Version of iOS on a Device
You should test your iOS application on devices running the version of iOS version targeted by the SDK you’re
using. The devices organizer enables you to restore a currently installed version of iOS or to install a new
version.
Install a new version of iOS when you want to upgrade a device for development.

To restore or install iOS on your development device . . .
1.

Select the device you want to update from the Devices organizer.

2.

Select an iOS version from the Software Version pop-up menu.

3.

Click the Restore button, and confirm you want to install the software.

4.

When installation is complete, activate the device and restore its contents using iTunes.

5.

Back in Xcode, click “Use for Development” in the Devices organizer to reenable development for the
device.


You may need to install iOS on your development device to run your app on a beta or GM version of the
iOS software.


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Manage Your Devices
Run Your Application On the Device

The Software Version pop-up menu displays the versions of iOS that are available for you to install. If the
version you want is not listed, you must add it to this menu before you can install it. To add the new software
version to the menu, select Other Version and navigate to the software image on your computer. Xcode
then adds the version to the pop-up menu and makes it available for installation.
When you enable a device for development, Xcode installs any provisioning profiles and development-related
data associated with the device. Xcode asks you for your developer program credentials and provisions
any new devices automatically before making them available for development.
Important: The version of iOS you install must be the same as or newer than the version currently
installed on the device. Attempting to install an older software image will fail. After a failed installation
attempt, you must reinstall the last successfully installed version or a newer version of iOS.

Note: You can download seed releases of the iOS SDK and iOS, when they are available, from the
iOS Dev Center.

Set the run destination to iOS device in the scheme editor and build and run your application. Xcode transfers
the application to the device and executes it.

Remove an Application from a Device
Successful development and testing frequently depend on starting with a clean execution environment. To
achieve this state, you can completely remove your application from a device.
Delete an app from your device to remove all data files associated with the app.

To remove your application from a device . . .
1.

In the Devices organizer, select Applications in the device.

2.

Select an app from the list of installed apps.


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Manage Your Devices

3.

Click Delete, and confirm that you want to remove the app.

During development, you might remove an app in order to test code that runs only when your app is first
launched.
From Xcode, you can remove only the apps that you created. You cannot remove any of the system-installed
or third-party apps from the device using Xcode.


231

Manage Your Devices

Alternative: Another way to remove a third-party app (including your own) from a device is to
touch and hold the app icon on the device until the icons start wiggling. Then tap the close box
on a given app to remove it from the device. When you are done, press the Home button.

Download Your Application’s Data for Analysis
You probably have favorite tools that you use in inspecting application-generated data. To use such tools, you
need to copy that data to your computer intact. To do so, you download the data from the devices organizer,
specifying a location for the data on your local file system.
Copy an app’s data from its sandbox on an iOS device to your file system to examine or modify the data.

To download your application’s data from a device . . .
1.

In the Devices organizer, select Applications in the device.

2.

Select the app.

3.

Click Download.


232

Manage Your Devices

4.

Specify the name and location of the app-data package.


233

Manage Your Devices
Capture and Use Screenshots from a Device

When you copy the app data, the app itself is not copied, and neither is any data the app stores in the
keychain.
Analyzing the contents of an app’s sandbox may provide important information to help you diagnose
problems or tune the app. You can examine files that the app created—or that it obtained from an external
source—to find out whether the files contain valid information or indicate a problem.

Screenshots are important in several aspects of development and distribution—for example, serving as
illustrations in documentation and as graphics for the App Store and other marketing needs.
In the organizer you can capture and manipulate screenshots of your application running on the device.
Capture a screenshot on your device to document your progress during development, and create launch
images for your iOS apps.

To capture screenshots from a device . . .
1.

On the device, configure the screen the way you want it.

2.

In the Devices organizer, select Screenshots in the device.


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Manage Your Devices

3.

Click New Screenshot.

When generating your app’s default images, you should always capture images from devices with the
appropriate screen size and resolution. For a universal app, this means capturing screenshots both from
an iPad and from an iPhone or iPod touch. For an app that also supports Retina displays, it means capturing
screenshots from an iPhone 4 in addition to any other devices.

Set a Screenshot as Your iOS Application’s Launch Image
An application launch image, or default image , enhances the user’s experience at application launch. When
the user starts your application, iOS immediately displays this image. Your application then displays its first
screen as soon as possible, replacing the launch image.
Set the launch image of your app to give the user immediate feedback that the app launched.


235

Manage Your Devices

To set a screenshot as your iOS application's default image . . .
1.

In the Devices organizer, select Screenshots for a device or for the Library section.

2.

Select an image.

3.

Click “Save as Launch Image.”

4.

Specify the name of the image and the target app, and click Next.

A launch image acts as a placeholder for your app’s user interface at launch time. When the user launches
your app, the iOS presents this image until your app displays its main window and starts responding to
events.
An iPhone app has only one launch image, typically named Default.png. An iPad app can have multiple
launch images, each one presenting the app’s user interface in a specific device orientation. Launch images
may have names other than Default.png.


236

Manage Your Devices

To help avoid a jarring experience when this switch occurs, the ideal default image looks identical to the first
screen your application displays, except that it should omit any UI elements that could change.

Export a Screenshot to Your File System
To use a screenshot outside your application, for example, in documentation or marketing materials, you can
export it from within the devices organizer.
Save a screenshot to your file system to archive it or use it for materials related to your app.

To export a screenshot to your file system . . .
1.

In the Devices organizer, select the appropriate Screenshots group.

2.

Select the screenshot, and click Export.

3.

When prompted, enter a name and location for the screenshot, and click Save.


237

Manage Your Devices

You may want to provide one or more screenshots of your app when submitting it for publication on the
App Store.
Saved screenshots are exported as high-quality PNG files.
With the screenshot file on your computer file system, you can modify it with any graphics editing application
that accepts PNG files.

Identify Small UI Changes by Comparing Screenshots
As development progresses, small changes you have made to your UI may be unrecorded and remain unnoticed
until late in the development cycle. To help mitigate this problem, you can compare different versions of a
screenshot to determine exactly what has changed.
Compare screenshots to detect subtle changes to your user interface.

To compare screenshots . . .
1.

In the Devices organizer, select the appropriate Screenshots group.

2.

Select two or more screenshots.

3.

Select the Compare option.


238

Manage Your Devices
Transfer Your Developer Profile to Another Computer

4.

Use the Tolerance slider to adjust the comparison threshold.

The screenshots you select must be the same size and at least somewhat similar. You cannot compare
screenshots whose resolution or dimensions are different. For example, you cannot compare a screenshot
taken on a Retina display with one taken on a lower-resolution display. If the content of the screenshots is
completely different, the Compare option is not available.

Your developer profile is your official digital identification for iOS application development. If your development
workflow requires you to use another user account or another computer, you must copy that profile to that
other account or computer.


239

Manage Your Devices

To do so, you first export your profile, which archives the profile into a password-protected secure file in a
location that you specify on your operating system. This export is performed in the devices organizer.
Archive your code signing assets to keep them safe or to use them on another Mac.

To export your developer profile . . .
1.

In the Devices organizer, select your team in the Teams section.

2.

Click Export.

3.

Specify a filename and a password, and click Save.


240

Manage Your Devices

The file produced contains the items you need to code sign apps, including the provisioning profiles,
certificates, and private keys needed to install apps in development on a device.
Because it contains sensitive information that can be used to sign apps in your name, the contents of the
file are stored in an encrypted format using the password you provide. That password is required later to
import the file to another system.
Next, you copy the archive file to the other account or computer.
Finally, in the other account or on the other computer, you use the devices organizer to import your profile
by extracting it from the archive file.
Place your code signing assets on a new Mac by importing the code signing assets exported from another
Mac.

To import your developer profile . . .
1.

In the Devices organizer, select your team in the Teams section.

2.

Click Import.

3.

Select the file containing your code signing assets.


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Manage Your Devices

4.

Enter the password for the file, and click Open.

The importation process installs the certificates, private keys, and provisioning profiles that are stored in
the developer-profile file.
Troubleshooting: If you don’t see the Team section in the devices organizer:
●

Drag the password-protected file that contains your code signing assets to the Xcode icon
in the Dock.


242

Manage Your Devices

Finally, in the other account or on the other computer, you use the devices organizer to import your profile
by extracting it from the archive file.


243

Save and Revert Changes to Files

As you create your app, Xcode automatically saves changes to source, project, and workspace files. This feature
simplifies workflow, helps keep you from losing any of your work, and requires no configuration.
When creating an app, sometimes you may want to experiment with a new user interface layout and then
revert to the previous one. Or you may need to undo some code that you’ve just written because you found
an error or problem. These circumstances require that you understand how Xcode saves your work to disk and
know how to revert your work to a prior state.
This chapter explains how Xcode automatically saves your work and shows how to use the Revert Document
and Undo commands. The Snapshot feature is introduced as well as Xcode’s built-in interface to source code
management so that you understand how they relate to the overall tasks of change management in your
development projects.

Save when Editing
As you edit, Xcode continuously tracks changes and saves them, but it does not continuously write the changes
to disk. They are saved in memory as you work. Xcode then automatically writes your changes to disk when
one of five operations is performed:
●

You build and run your app.

●

A snapshot is created.

●

You commit files to an SCM repository.

●

You close the project.

●

You quit Xcode

You can also save changes to disk manually using the Save command in the File menu.

Revert to the Last Saved Version
To discard all changes you’ve made to a file since it was last saved, use the Revert Document command in the
File menu. After a confirmation dialog appears, click the Revert button to complete the operation.


244

Revert to the Last Saved Version

The Revert Document command is available only when the contents of a file have been changed since it was
last saved to disk. Files with in-memory changes are indicated in two places: The file icon is highlighted in the
project navigator and in the associated editor pane’s jump bar. Highlighted icons in the project navigator let
you see which files have in-memory changes throughout the entire project. The highlighted icon in an editor’s
jump bar indicates whether any changes to the document currently in view were made since it was last saved.
For example, in Figure 10-1 you see a workspace window with the file MainMenu.xib open in the primary
editor and three text files (Controller.h, Controller.m, and ReadMe.txt) open in assistant editors.
Figure 10-1

Workspace window with in-memory changes to files
Open with changes

Three of the four files open in Figure 10-1 have changed since they were last saved, indicated by the highlighted
icons in the jump bars and in the project navigator. The Revert Document command allows you to revert to
the last saved version of each file, one at a time. It acts on the file that currently has the editing focus, obtained
by clicking in its editor pane or by clicking its name in the project navigator. In this illustration, MainMenu.xib
has the editing focus, which you can tell by the slightly darker coloring of the jump bar in the primary editor.
Using Revert Document in Xcode always returns the contents of the file to the last saved version on disk. If
you are not sure when the file was last saved to disk relative to when you made changes, or you would prefer
to back out changes one at a time, use the Undo command in the Edit menu.


245

Undo Changes Incrementally

Undo Changes Incrementally
To back out changes to a file incrementally, use the Undo command in the Edit menu, shown in Figure 10-2.
Figure 10-2

Undo Typing command

Note: The Undo command is context sensitive to the last editing operation performed. For example,
the command changes from Undo to Undo Typing or to Undo Add Menu Item depending on the
context of the last operation performed.
After you’ve chosen the Undo command, the Redo command becomes available to reverse the last
undo operation.

The Undo command in Xcode allows you to incrementally back out all changes to a file since the start of an
editing session. An editing session begins when you open a project with Xcode and ends when you close the
project. When you work on a file in a single session, Xcode lets you undo all the edits in that session, even
those already saved to disk.
When you work in a text document and choose Undo, the source editor sets the insertion point to the affected
section of the text and brings that section into view. In this way, you know the change that the Undo command
has undone.


246

Unlocking Files

Note: Using the Revert Document command clears the Undo history; you cannot undo a revert
operation.

Unlocking Files
Files included in a project may be locked for several reasons. For example, they may be header files included
in system frameworks, or they may have been intentionally locked in the Finder to prevent accidental deletion
and renaming. Locked files cannot be edited; they are available only for reading, searching, and selecting
portions to copy.
If you attempt to edit the contents of a locked file, Xcode presents a notification asking whether you want to
unlock the file. Click the Unlock button to continue the unlocking operation. If the file cannot be unlocked,
you receive another notification (see, for example, Figure 10-3).
Figure 10-3

File could not be unlocked


247

Unlocking Files

Locked files are indicated in the Xcode workspace by a locked file icon in the project navigator or by a lock
icon in the associated editor pane’s jump bar. The locked file icon also appears in the workspace window title
when the document is in the primary editor pane (see Figure 10-4).
Figure 10-4

Locked file indicators
Locked file icon

Locked file icon

Lock icon

Note: The locked file icon appears in the project navigator only for files that are locked in the Finder.
Files locked for write access due to ownership permissions or read-only media show the lock icon
in the jump bar.

When you start editing a locked file, Xcode asks whether you want to unlock it. You can also unlock a file by
using the Unlock command in the File menu or by clicking on the lock icon in the jump bar of its associated
editor pane.


248

Use Snapshots and SCM for Projectwide Change

When you develop a project, you often make changes on a larger scale than changes to individual files. The
snapshot and source code management systems provide save and revert facilities that operate project wide.

Snapshots Archive Projectwide Changes to Documents and Configuration
Use the Create Snapshot command in the File menu to create an archive of the project or workspace.
You can make three types of projectwide changes for which the Revert Document and Undo commands are
not supported:
●

●

●

Xcode projectwide operations, which involve changes to many document files and potentially to project
settings. These operations include refactoring code, adding Automatic Reference Counting to an existing
project, and performing project validation.
Adjustments to the workspace and project settings. Xcode saves these changes to disk as they are performed
by modifying the .xcodeproj and .xcworkspace files.
Your global editing operations using search and replace functions.

Snapshots are archives that include the current state of all project and workspace settings and all document
files included in the project context. All document files are saved when a snapshot is created. Xcode always
stores snapshots in your local file system.
Creating a snapshot before making changes to project settings, and before using global search and replace,
gives you the ability to revert the entire project to the state it was in before you performed a projectwide
operation.
Note: Xcode automatically creates a snapshot of the project before performing refactoring, automatic
reference counting conversion, and validation.

For more information about snapshots, see "Save and Revert Changes to Projects" (page 251).

SCM Repositories Manage Overall Change as Your Project Develops
The Source Control commands in the File menu allow you to manage your project files with a source code
management (SCM) repository.
Automatic save, revert, undo, and snapshots are intended to help the flow of editing and making adjustments
as you develop your project with respect to the document files it includes. These features are not intended to
be the way you manage overall project change through the development history of a project. To support this


249


larger scope of managing change in your development work, Xcode provides built-in access to source code
management commands that allow you to use both locally stored and server-based SCM repositories. Using
an SCM repository is strongly recommended even for small development projects.
For more information about using source code management, see "Save and Revert Changes to Projects" (page
251).


250

Save and Revert Changes to Projects

Xcode provides several ways to save versions of your project:
●

●

●

A snapshot saves the current state of your project or workspace on disk for possible restoration later.
Source control repositories keep track of individual changes to files and enable you to merge different
versions of a file.
An archive packages your products for distribution, either through your own distribution mechanism or
for submission to the App Store. See "To create a workspace" (page 62) for details.

Xcode provides direct support for Git and Subversion repositories, including an option to create a local Git
repository when you create a new project. Because it’s so easy to set up a repository to use with your Xcode
project, Xcode provides a special editor, called the version editor , that also makes it easy to compare different
versions of files saved in repositories.
This chapter assumes that some developers using Xcode are new to repositories. If you’re an experienced
repository user, skip over the introductory material in each section and go straight to the descriptions of aspects
of Xcode’s repository UI.


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A snapshot provides an easy way to back up the current version of your project or workspace so that, if
something goes wrong with a change or process, you can restore the earlier version. Xcode can create a
snapshot automatically before a major change such as refactoring your code or executing a Find and Replace
operation. You can change this setting any time in the Snapshots pane of the File > Project Settings or File >
Workspace Settings dialog (Figure 11-1).
Figure 11-1

The Snapshots settings dialog

You can also set Xcode to automatically create snapshots in other circumstances, such as before a build, by
selecting the Create Snapshot option in the Behaviors pane of Xcode preferences ("Customize Your Build and
Run Workflow" (page ?)).
You can create a snapshot manually whenever you like by choosing File > Create Snapshot. To see where
Xcode stores your snapshots, or to change the location, look in the Locations pane of Xcode preferences or
the Snapshots pane of the Project (or Workspace) Settings dialog.
Important: To use snapshots, you must have selected System Tools in the Xcode installer. This option is
selected by default.
To see the snapshots for a project or workspace, click the project in the projects organizer. To restore from a
snapshot in Xcode 4.0, select a snapshot in the projects organizer and click the Restore Snapshot button at
the bottom of the window.
In Xcode 4.1 and later, to restore a snapshot, choose Restore Snapshot from the File menu and select the
snapshot to restore. Xcode displays a preview dialog in which you can review the differences between the
current version of the project and the snapshot version. When you click Restore, Xcode replaces the current
version of the project with the version in the snapshot. Xcode makes a snapshot of the current version before
replacing it.


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Keep Track of Changes with Source Control

To restore a snapshot in a new location instead of restoring on top of the current project, select the project in
the Projects pane of the Organizer window, choose the snapshot you want to restore, and click the Export
Snapshot button at the bottom of the window (Figure 11-2).
Figure 11-2

Snapshots listed in the Organizer window

Because Xcode 4 keeps track of all your projects and displays them in the projects organizer even if they no
longer exist, you can restore a deleted project from a snapshot.

When working on a software project, it can be very useful to use software control management (SCM) to keep
track of changes in the code and coordinate work groups. An SCM system, also referred to as source control ,
saves multiple versions of each file on disk, storing metadata about each version of each file in a location known
as an SCM repository .

Why Use Source Control?
There are two fundamental reasons for using source control:


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●

●

A source control system helps you reconstruct past versions of the software and the process used to
develop it. If you are working on a project by yourself, you can commit a file to your SCM repository each
time you make a major change. Then, if you find you’ve introduced bugs, you can compare the new version
with a past version that worked correctly to help to locate the source of the trouble. In the worst-case
scenario, you can revert to an earlier version and start over from there to reimplement the new feature. If
you keep your repository, or a copy of the repository, in another, physically safe location, you can even
reconstruct your project if your computer is lost or destroyed.
When two or more people are working on the same project, source control helps prevent conflicts and
helps resolve conflicts should they arise. By keeping a central repository that holds the canonical copy of
the software, the source control system allows each programmer to work on his or her own local copy
without any danger of corrupting the canonical version. If you set up a system of checking out a file before
working on it, you can ensure that two people are not working on the same code at the same time. If two
people do change the same code, the SCM software helps you to merge the two versions. You can also
look through past changes to see what they were and who made them, which can be a great help in
managing the project and in fixing bugs.

Choose Git or Subversion
Xcode supports two SCM systems: Subversion (often abbreviated svn) and Git. Subversion is always server-based
and the server is normally on a remote machine, though it is possible to install one locally. Git can be used
purely as a local repository, or you can install a Git server on a remote machine to share files among team
members. The Xcode 4 installer installs the Git and Subversion tools when you select System Tools.
If you are working alone, it’s generally easiest to use Git, as you don’t need to set up a server. In fact, Xcode
can automatically set up a Git repository for you when you create a new project (see "Create a Git Repository
For Your New Project" (page 58)). For a group project, the choice of Subversion or Git is usually a matter of
taste and prior experience.
In so far as is possible, Xcode provides a consistent user interface and workflow for users of either Subversion
or Git.

Learn SCM Terminology
In general, you work on a copy of the project (called, appropriately, a working copy ). The command to create
a working copy is clone for Git and checkout for Subversion. When you have changed one or more files and
want to add your changes to the repository, you execute a commit command to the SCM software. The SCM
software records the date and time of the commit, any comments you include to help you remember later
why you committed this version of the code, your identity (that is, the identity of the person who executed
the commit command), and any other information the SCM software needs in order to keep track of the
software.


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Because Subversion repositories always reside on a server, when you commit changes to your project, Xcode
sends those changes back to the server. Because Git repositories can be local or on a server, the situation is a
bit different with Git. For Git, your working copy is also a local repository, so once you’ve committed the file,
the repository has been updated. Even if you have a remote Git server, committing a file in Git does not
automatically send changes to the server. To update the Git repository on a remote server, you use a push
command.
To update your working copy with the latest version of the file in a remote repository, you use a pull command
(in Git) or update command (in Subversion). For a local Git repository, the pull command is not needed.
The main line of code for development is often referred to as the trunk . To avoid modifying the trunk while
developing new features, you can create a new copy of the project referred to as a branch . Eventually, branches
are merged back into the trunk. In Git, a branch is simply a working copy of the project. In Subversion, a branch
is a copy maintained by the repository. You can check out any number of working copies of a Subversion
branch. When you update your local working copy with the update or pull command, and when you merge
two branches or merge a branch into the trunk, Xcode displays a dialog that lets you reconcile differences
between the versions. You can also use the version editor to compare two versions of a file at any time.


255


Manage Your Repositories
In Xcode, you configure SCM repositories in the Organizer (Figure 11-3).
Figure 11-3

The repositories pane in the Organizer window

The repositories pane of the Organizer window (referred to hereafter as the repositories organizer ) lets you
examine the structure of the repository (folders, files, and branches) and your working copy. In addition to the
more obvious features provided by the repositories organizer, it lets you assign address-book information to
the person who committed each version listed and you can examine the changes to each file for each commit.

To assign address book information to identities in the organizer
1.

Click a repository in the navigation pane of the repositories organizer.


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2.

Click the icon well next to the commit ID number.

3.

Fill in the information about the person who executed the commit, or if the person is in your address
book, click Choose Card and select that person’s card in your address book. If your address book has
a picture associated with the entry, the picture is displayed in the organizer.


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View files in a specific commit version to inspect changes that you have made to those files.

To view changes for a specific commit version . . .
1.

In the navigation pane of the repositories organizer, select the working copy folder of the project.

2.

Click the disclosure triangle next to the commit ID number.

3.

Click View Changes.

4.

Select a file in the navigation pane.

5.

Scroll, if necessary, to view changes in the file.


Clicking the disclosure triangle for a commit version reveals a list of changed files, allowing you to quickly
scan for the one you want to inspect.
In the inspection dialog, Xcode displays the changes between the file you have chosen and the previous
commit of the same file. For convenience, each change is highlighted in the editor pane and indicated by
a red mark in the scroll bar.
The video shows viewing changes in the SKTLine.h file in the most recent commit version of the
Skecth_git_M repository.

Find SCM Commands
SCM commands are located in the main Xcode menu, in the shortcut menu, and in the repositories organizer.


258


Source control commands are in the Source Control submenu of the File menu (Figure 11-4).
Figure 11-4

The Source Control submenu of the File menu

The project navigator shortcut menu contains a subset of these commands (Figure 11-5).
Figure 11-5

The Source Control submenu of the project navigator shortcut menu

Many SCM commands can be executed by using buttons at the bottom of the repositories organizer. Which
buttons are available and active depends on your selection in the navigator pane of the repositories organizer.
For example, Figure 11-6 shows the buttons at the bottom of the repositories organizer when a git working
copy is selected.
Figure 11-6

Repositories organizer buttons

Update and commit operations are recorded in the log navigator. Select a log to see the individual steps of
that operation in the log viewer.


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Keep Track of Your Files’ SCM Status
You can keep track of your files’ SCM status in the project navigator. SCM status is shown as a badge next to
the file name (Figure 11-7), as follows:
Badge

SCM status

M

Locally modified

U

Updated in repository

A

Locally added

D

Locally deleted

I

Ignored

R

Replaced in the repository

–

The contents of the folder have mixed status; display the contents to see individual status

?

Not under source control

Figure 11-7

Source control badges in the project navigator

Badges propagate up to the highest container so you can see the source control status of the whole workspace
regardless of the disclosure level. Detailed SCM status is shown in the Source Control area of the File inspector
in the utility pane.


260

Work with Git and Subversion

Common source control tasks include setting up a repository, checking files out of and in to a repository,
reconciling different versions of a file, and using branches to isolate risky changes to your code.

Set Up Git Version Control When You Create a New Project
As described in "Create a Git Repository For Your New Project" (page 58), Xcode creates a Git repository for a
new project if you select the Source Control option in the Save As dialog. When you do so, Xcode adds a hidden
file (named .git) to the folder containing the project. That file contains all the information Git needs to keep
track of the files in the project and the changes made to them. Xcode also performs an initial commit of the
files in the folder. Any time you add files to your project or modify any of the files in the project, you need to
commit them to add them to the repository (see "Commit Files to Add Them to a Repository" (page 271)).

Add Git or Subversion Version Control to an Existing Project
You may need to create your own repository if, for example, you want to start managing an existing project
under source control. You can use command-line tools to set up a Git or Subversion repository. The necessary
tools are installed during Xcode installation, if you select the System Tools package.
Use command-line commands to set up a Git repository for an existing project.

To set up a Git repository from the command line . . .
1.

Use the cd command to switch to your project directory, making it the current working directory.

2.

Enter git init to create an empty repository.

3.

Enter git add . to copy your project files into the repository.

4.

Enter git commit -m "Initial commit" to commit all the files.

// Step 1
$ cd /Users/me/sample_code/Sketch

// Step 2
$ git init
Initialized empty Git repository in /Users/me/sample_code/Sketch/.git/

// Step 3
$ git add .


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// Step 4
$ git commit -m "Initial commit"
[master (root-commit) 173067e] Initial commit
...
74 files changed, 10198 insertions(+)
create mode 100644 .DS_Store
create mode 100644 Arrow.tiff
create mode 100644 Circle.tiff
create mode 100644 Cross.tiff
create mode 100644 Draw2App.icns
create mode 100644 Draw2File.icns
create mode 100644 English.lproj/Draw2.nib/classes.nib
...
create mode 100644
Sketch.xcodeproj/xcuserdata/ernest.xcuserdatad/xcdebugger/Breakpoints.xcbkptlist
create mode 100644
Sketch.xcodeproj/xcuserdata/ernest.xcuserdatad/xcschemes/Sketch.xcscheme
create mode 100644
Sketch.xcodeproj/xcuserdata/ernest.xcuserdatad/xcschemes/xcschememanagement.plist
create mode 100644 TextGraphic.tiff

To set up a repository for an existing project, you have to use the command-line shell implemented by the
Terminal utility app.
Use command-line commands to set up a Subversion repository.

To set up a Subversion repository from the command line . . .
1.

Use the mkdir command to create a directory with three subdirectories named branches, tags, and
trunk to hold a temporary copy of your project.

2.

Copy the project directory into the trunk subdirectory.

3.

Create a directory for the Subversion repository.

4.

Use the svnadmin create command to create an empty Subversion repository.

5.

Use the svn import command to import your project directory into the new Subversion repository.

// Step 1


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$ mkdir /Sketch_svn_tmp
$ mkdir /Sketch_svn_tmp/trunk
$ mkdir /Sketch_svn_tmp/branches
$ mkdir /Sketch_svn_tmp/tags

// Step 2
$ cp -R /Users/me/sample_code/Sketch /Sketch_svn_tmp/trunk

// Step 3
$ mkdir /svn_rep

// Step 4
$ svnadmin create /svn_rep/Sketch_svn

// Step 5
$ svn import /Sketch_svn_tmp file:///svn_rep/Sketch_svn -m "Initial import"
Adding

/Sketch_svn_tmp/trunk

Adding

/Sketch_svn_tmp/trunk/Sketch

Adding

/Sketch_svn_tmp/trunk/Sketch/SKTGraphicView.h

Adding
Adding

(bin)

/Sketch_svn_tmp/trunk/Sketch/Cross.tiff
/Sketch_svn_tmp/trunk/Sketch/SKTAppDelegate.h

...
Adding

/Sketch_svn_tmp/trunk/Sketch/NSColor_SKTScripting.m

Adding

/Sketch_svn_tmp/branches

Adding

/Sketch_svn_tmp/tags

Committed revision 1.

To set up a Subversion repository, you have to use the command-line shell implemented by the Terminal
utility app.
If you don’t have an existing project, use Xcode to create a project before setting up your repository.


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Note: By convention, a Subversion repository contains three additional subdirectories named
branches, tags, and trunk.

Clone or Check Out a Copy of a Project to Use Locally
If you or your work group have a Subversion server or a master copy of a Git repository shared on a file server,
you can create a local working copy by checking out (Subversion) or cloning (Git) a copy of the master. You
can then use the source control commands in Xcode to commit changes to your local copy, update your local
copy from the master copy, and push your changes up to the master copy (for Git). Note that it is not necessary
to clone a copy of a local Git repository, as in this case the master copy is also your working copy.
Check out or clone a repository to create a copy on your local system.

To check out or clone a repository . . .
1.

In the repositories organizer, click the Add button and choose Checkout or Clone Repository.

2.

Enter the pathname or URL for the file.

3.

When the “Host is reachable” indicator turns green, click the Next button.

4.

Enter a local name for the repository and click Clone (or Checkout) to copy it.

5.

Choose a location and click the highlighted Clone (or Checkout) button to save the local repository.


By abstracting common repository operations, Xcode supports both Git and Subversion (SVN) repositories
with a single, unified graphical user interface and workflow. Depending on your choice, this one operation
checks out (for SVN) or clones (for Git) the repository and integrates it with your project.
Cloning a Git repository in Xcode sets up a complete repository on your local system and integrates that
repository with your workspace so that you can quickly start using it. This approach gives you the benefits
of distributed version control, including full commit rights, whether you’re online or not.
An SVN checkout operation does not create a local repository. You must have a network connection to the
repository server to be able to commit changes.


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For SVN, you must also provide the relative paths to the trunk, branches, and tags directories. To do
so, click the name of the new repository in the repositories organizer and fill in the associated fields. If your
SVN server requires authentication, fill in the user name and password as well.
The video shows cloning a Git repository for the Sketch sample code project.

Add an Existing SCM Working Copy of a Project to Xcode
If you have a working copy of a project that was checked out of Subversion or cloned from Git using the
command line or another tool, you can add it to your Xcode SCM repository support. To do so, click the Add
button (+) at the bottom of the navigation pane in the repository organizer and choose Add Working Copy.

Create a Branch to Isolate Risky Changes
After you’ve been working on a project for a while, you are likely to have a body of reliable, stable code.
Although a repository enables you to revert to an earlier version if you destabilize your program while attempting
to add a new feature, you might want to be able to work on the new feature while still maintaining your stable
body of code. That way, one of the members of your team can (for example) work on refining the user interface
or fixing minor bugs while another team member works on a risky new feature. In order to implement such a
scheme, most source control systems (including Git and Subversion) allow you to create a branch, which is
another copy of your code that you can modify independently of the original body of code (or of any other
branches). You can base a branch on the trunk or on any other branch.
Subversion keeps all the information about branches, submissions, updates, and so forth on the server. You
need to be connected to the server to see any of this information in Xcode. In Git, when you clone a repository,
you get a copy of all of the metadata associated with the repository as well as copies of all the existing branches.
To see the structure of a Subversion repository without checking out a working copy, or to see the branches
of a remote Git repository so you can clone an individual branch, use the Add Repository menu item (see "Clone
a Specific Branch" (page 268)).
Create a branch in a repository to isolate specific aspects of your software development efforts and to work in
parallel with other developers.

To create a branch in a Git repository . . .
1.

In the repositories organizer, select the appropriate Branches directory in the navigator pane and click
the Add Branch button.

2.

Enter a name for the new branch.

3.

From the pop-up menu, choose an existing branch to serve as the starting point for this new branch.

4.

If appropriate, select the option to automatically switch to the new branch.


265


5.

Click Create.

Git creates the new branch in your local repository. To make the branch available to others on a remote
Git repository, you need to use the Push command.
The illustration shows adding a branch named Third , using the branch named Second as a starting point.
Important: Consistent branching practices are critical to successful source control management. Be
sure to understand and adhere to your organization’s branching strategy.
Create a branch in a repository to isolate specific aspects of your software development efforts and to work in
parallel with other developers.

To create a branch in a Subversion repository . . .
1.

In the repositories organizer, select the appropriate Branches directory in the navigator pane and click
the Add Branch button.


266


2.

Enter a name for the new branch.

3.

From the pop-up menu, choose an existing branch to serve as the starting point for this new branch.

4.

Enter a log message if you wish.

5.

If appropriate, select the option to automatically check out the new branch.

6.

Click Create.

Subversion creates the new branch in the remote repository; to work on it locally, you must first check it
out. Selecting the “Automatically checkout this branch” option causes Xcode to check it out for you. If you
select this option, Xcode opens a Save As dialog so you can specify the name and location for the working
copy of the new branch. If you do not select this option, you have to check out the branch before you can
work with it.
The illustration shows adding a branch named Sixth , using the branch named Fifth as a starting point.


267


Important: Consistent branching practices are critical to successful source control management. Be
sure to understand and adhere to your organization’s branching strategy.
Switch to another branch of a repository to work on a different line of code development or to prepare for a
branch merge.

To switch branches . . .
1.

In the navigation pane of the repositories organizer, click the working copy folder for the repository.

2.

Click the Switch Branch button at the bottom of the Organizer window.

3.

In the Select a Branch dialog, choose the branch you want to use from the pop-up menu.

4.

Click OK to confirm the switch.


When the working copy of a branch is selected in the navigation pane, the name and location of the current
branch display at the top of the organizer pane. When the switching operation is successful, this designation
updates to reflect the new current branch.
The video shows switching from the Henchley_01 branch to the Cardiff_02 branch of the Sketch
svn_M repository.

Clone a Specific Branch
Rather than clone an entire remote repository, you might want to clone only a specific branch. Use the Add
Repository command for this purpose. You can also use the Add Repository command to browse a Subversion
repository without creating a working copy.

To clone specific branches of a remote repository
1.

Open the repositories organizer, click the Add button (+) at the bottom of the navigator pane, and
choose Add Repository.


268


2.

In the Add a Repository dialog, fill in a name for your local working copy and the location of the remote
repository. Click Add.

3.

Select the branch for which you want a local working copy and click Clone.


269


Add a Folder to a Subversion Repository
When you select a folder such as Trunk for a Subversion repository in the navigation pane of the repositories
organizer, or any folder in the outline view of a Subversion repository, a New Directory button is available at
the bottom of the window. This button creates a new directory, represented as a folder in the organizer. If no
folder is selected in the outline view, the folder is created at the same level as the top-level folders in the outline
view. If a folder in the outline view is selected, the new folder is created inside that folder.
Tip: Xcode provides the New Directory button in the repositories organizer to help you administer your Subversion
directory. It’s not intended for modifying your Xcode project. To add a folder to a project, use the project navigator
in the workspace window.

Once you create a new Subversion directory, you can add files to it.
Add nonproject files to a repository folder created with the repositories organizer.

To add files to a new Subversion directory . . .
1.

In the repositories organizer, select the folder to which the files will be added.

2.

Click the Import button at the lower right corner of the window.

3.

Locate and select the desired file or folder.

4.

Click Import.

5.

Enter a commit message and click Import.


The repositories organizer supports creating a folder in a subversion repository for maintaining and
administering the repository. For example, you might want to include documents that provide details for
a specific branch or that specify any deviations from your organization’s branching and merging protocols.
To add folders and files to a project, use the project navigator in the workspace window.


270


Alternative: You can drag files to the folder from the Finder. If you use this approach, an Import
dialog appears in which you can add an import message and confirm the operation.

The video shows adding the file Branching_conventions_and_protocols.txt to the Admin_Docs
Subversion directory.

Commit Files to Add Them to a Repository
When you edit a file, it is changed locally but the changes are not included in the source control repository.
To add the changes to the repository, you must commit the file. You must save the file before you can commit
it, but note that saving a file is not the same as committing it to source control—you must explicitly commit
the file. To see which files have been modified locally but not committed, look for the M badge next to the
filename in the project navigator. (New files that have never been committed to source control have the A
badge. Files that are not under source control have a question mark badge.) You can use the SCM status filter
at the bottom of the project navigator to display only files with SCM status.
Commit changed files to ensure that those changes are preserved and managed as part of a repository.

To commit files to a repository . . .
1.

Ensure that you have saved all file changes.

2.

Choose File > Source Control > Commit.

3.

In the confirmation dialog, deselect any files that you do not wish to commit.

4.

Review and edit (as appropriate) any changes to be committed.

5.

Enter a commit comment.

6.

Click Commit.


You can use the confirmation dialog to compare your new version with any past version and to make any
necessary edits in the current version. Any changes you make as you review a file are included in the
committed file and saved in your project.


271


If you’re using Subversion, a commit operation copies the changes from selected files into the remote
Subversion repository. Therefore, you must be connected to the repository before you can commit changes.
(For details, see your repository administrator.)
If you’re using Git, the commit operation adds your changes to your local working copy. If you're using a
remote Git repository, you have to perform a push operation to add your committed changes to the shared
repository.
A commit comment is required; the Commit button is disabled until you enter one. Good comments are
specific, but concise; suggested content includes a brief description of the changes, what they are meant
to accomplish, and URLs or ID numbers of any relevant bugs. The version editor displays the affected code
together with your name and commit comment, so you can omit information that’s in code comments or
that’s obvious from looking at the line of code.
The video shows committing changes in four files in the Sketch project to a local Git repository.
Tip: To commit one or a small number of files, select those files in the project navigator,
Control-click one of them, and choose Source Control > Commit Selected Files from the shortcut
menu.

Alternative: You can select the working copy in the repositories organizer navigation pane and
click the Commit button at the bottom of the Organizer window.

Reconcile Different Branches
When you’re ready to merge the code in a separate branch back into the main branch, or when you want to
combine the code in any two branches, you can use the merge facility of your source control system to reconcile
differences between the branches.
Merge two branches to combine the code in them and reconcile differences between them.

To merge two branches . . .
1.

With the workspace window active, choose File > Source Control > Merge.

2.

From the pop-up menu, choose the branch to merge into the current branch and click Choose.

3.

Select a difference or conflict.

4.

Use the left and right buttons to specify which file’s contents should be used.


272


5.

After resolving all differences and conflicts, click Merge.


Before merging, save and commit any unsaved changes in both branches. The Merge command merges a
branch that you choose into the current branch, so you may also need to switch the current branch before
the merge operation.
The left pane of the merge dialog shows what the merged file will look like. The right pane shows the file
with the changes to be merged in. For each difference between the files, an indicator in the center points
to the file taking precedence. To select a difference, click its indicator. You use the buttons at the bottom
to set the direction of the merge.
For example, if the difference is a line of code on the right that’s missing from the file on the left (your
working copy) click the Right button (which sets the indicator to the right) to specify that the line of code
be included in the working copy when the merge is complete. Note that because the left pane shows what
the merged file will look like, you then see this line of code in both panes.
If a line of code has been changed in both versions of the file being merged, the differences are considered
a conflict and are shown in red. There are two additional buttons for reconciling conflicts by taking the
code lines from both files, either listing the ones in the left file first and those in the right file second, or
vice versa.
To reconcile any differences not handled by the four button choices, you can edit the file in the working
copy.

Update Your Working Copy from a Remote Repository
When two or more people are working on a automata project, from time to time you need to synchronize your
working copy with changes made in the remote repository. You use the Pull command in Git or the Update
command in Subversion to do so.
Use a pull operation to update local files with changes from a shared or remote Git repository to ensure that
your local repository is up to date.

To pull changes from a remote Git repository . . .
1.

Choose File > Source Control > Pull.


273


2.

In the Pull dialog, select a file in the navigation pane.

3.

Select a difference to reconcile by clicking its indicator.

4.

Use the left and right buttons to specify how the difference is to be reconciled.

5.

After reconciling all differences, click Pull to complete the operation.

Before you can push changes in your local repository to a shared repository, Git requires a pull operation,
in which you reconcile differences between the two repositories. This reconciliation helps prevent your
accidentally modifying or undoing other developers’ changes.
You need to save changes you’ve made and commit them to your local repository before pulling changes
from the shared repository.
In the Pull dialog, you select a difference by clicking the indicator between the two files. You then click one
of the four buttons at the bottom to choose how that difference is to be reconciled. The indicator updates
to reflect your choice.
A difference in which a line of code has been changed in both versions of the file is considered a conflict,
and its indicator is a question mark. You can’t complete the pull operation until you specify how to resolve
all conflicts.


274


If you wish, you can edit the local revision of the file in the Pull dialog to reconcile any differences not
handled by the four button choices.
In busy times , multiple developers may attempt to submit changes to the shared repository at the same
time. If another developer’s submission completes before yours, Xcode informs you that you must first
perform a new pull operation. In larger organizations, particularly just prior to a product release, you may
find that you have to pull changes more than once.
After the pull operation, you have to commit the changes files in your local repository that are updated by
the pull operation.
The illustration shows the Pull dialog, with a conflict selected.
Tip: To pull changes for one file or a small number of files, select those files in the project
navigator, Control-click one of them, and choose Source Control > Update Selected Files from
the shortcut menu that appears.

Update your local working copy with changes from a shared or remote Subversion repository to ensure that
your local copy is up to date.

To update changes from a remote Subversion repository . . .
1.

Choose File > Source Control > Update.

2.

In the Update dialog, select a difference to reconcile.

3.

Use the left and right buttons to specify which file’s contents should be used.


275


4.

After reconciling all differences, click Update to complete the operation.

With a shared repository, there is a potential for one developer’s changes to undo or overwrite those of
another developer. To prevent this problem, Subversion requires that you update your local copy with the
changes already submitted to the shared repository.
Note: You must have an active network connection to the server that holds the remote repository.

You need to save changes you’ve made and commit them to your local repository before updating files
with changes from the shared repository.
In the update dialog, you select a difference by clicking the indicator between the two files. You then click
one of the four buttons at the bottom to choose how that difference is to be reconciled. The indicator
updates to reflect your choice.
A difference in which a line of code has been changed in both versions of the file is considered a conflict,
and its indicator is a question mark. You can’t complete the update operation until you specify how to
resolve all conflicts.


276


If you wish, you can edit the local revision of the file in the update dialog to reconcile any differences not
handled by the four button choices.
In busy times , multiple developers may attempt to submit changes to the shared repository at the same
time. If another developer’s submission completes before yours, Xcode informs you that you must first
perform a new update operation. In larger organizations, particularly just prior to a product release, you
may find that you have to update more than once.
After the update, you have to commit the changes files in your local repository that are updated by the
update.
The illustration shows the dialog for reconciling differences, with a conflict selected.
Tip: To update one file or a small number of files, select those files in the project navigator,
Control-click one of them, and choose Source Control > Update Selected Files from the shortcut
menu that appears.

Send Your Working Copy to the Remote Git Repository
If you’re using a remote Git repository, when you’re ready to share your work with the other members of your
team, you can push your files back to the remote repository. (If you’re using Subversion, the commit command
updates the remote repository.) If you cloned your working copy from a repository, you should see the remote
repository in the repository organizer. Before performing a push, you have to save and commit all changes
and execute the Pull command to reconcile any differences between your version and the one on the server.
Then, choose File > Source Control > Push.


277

Compare Revisions

Save Internal Project Files in Repositories
In Xcode 4.1 and later, you can use repositories to view internal project files (for example, schemes and user
interface settings) when looking at SCM details in the SCM commit and update workflows. You can use this
facility to save and keep track of versions of project files in the same way as you save and keep track of source
files. Figure 11-8 shows a commit dialog displaying two versions of a scheme.
Figure 11-8

A scheme in the commit dialog

Compare Revisions
You use the Xcode version editor to compare revisions. To compare any two versions of a file under source
control in a side-by-side view, select the file in the project navigator and click the version editor button (
). Use the jump bar underneath either editor pane to select the version of the file to compare with
the one in the other pane (Figure 11-9). You can select any committed version of that file in any branch.


278

Compare Revisions

Buttons under the version editor (
) allow you to show a file comparison and timeline, change logs
for the file, or individual change annotations (“blame”) for each line of the file.
Figure 11-9

Comparing two revisions of a file with the version editor

You can edit the current working copy of the file in the version editor and you can copy code from an older
version and paste it into the current version.

Select Specific Revisions
Click the timeline icon (
) in the center column to show a visual timeline of all repository versions; use the
sliders to control which version is displayed on each side.
Use the version timeline to choose file versions based on their chronological order.

To compare versions of a file with the timeline . . .
1.

With a source file open in the version editor, click the Comparison button.

2.

Click the timeline viewer icon.

3.

Browse the timeline with your pointer to reach the version you want to compare.


279

Compare Revisions

4.

Click the right triangular indicator to open that version in the right editing pane.


The version timeline is available in the comparison view. Clicking the timeline viewer icon displays the
timeline between the two editing panes.
You move the pointer (cursor) up or down through the timeline to browse the available versions. Versions
are listed chronologically, with a line for each version; newer versions are at the bottom of the timeline.
Each major division in the timeline groups revisions submitted within a twenty-four hour period.
As you reach each version in the timeline, additional information for that version is displayed in an annotation.
When you find the version you want, click the left or right indicator triangle to display that version in the
corresponding editor pane. For example, the video shows choosing an older version of a file from the
repository (for display on the right) to compare it with the newer local version of that file (displayed on the
left).
Clicking the left indicator triangle allows you to compare another version in the left pane with the version
in the right.

Review Individual Changes
In blame mode, the current revision of the file is displayed along with the last revision that modified each line
of the file.

To see who is responsible for the last revision of a line of code
●

Click the blame mode button at the bottom of the version editor.


280

Compare Revisions

Each blame mode entry is aligned with the line in the file where the change was made. The entry
includes the name of the person who committed the change, the date, and the ID of the commit.

Tip: Next to the entry is an arrow button. Click the arrow next to any change that interests you to see
that change displayed in Comparison mode.

View All Revisions Chronologically
To review all revisions to a file listed in chronological order, use Log mode. Each change is listed individually,
and you can click the arrow next to the log entry to see the change displayed in Comparison mode.

To review all revisions to a file
●

Click the log mode button at the bottom of the version editor.


281

Distribute Your Program

All the log entries for the file are listed in chronological order and include the name of the person who
committed the change, the date, the ID of the commit, and the commit comments.

Tip: Click the arrow next to any entry to see that change displayed in Comparison mode.

Tip: You can view all the commits for a project, listed by file, in the Organizer window. See "Why Use Source

Control?" (page 277) for details.

Archives package your products for distribution. Use archives to distribute your program through your own
distribution mechanism or to submit an application to iTunes Connect for inclusion in the iOS or Mac app store.
To build your project and save the resulting application or a disk image of the set of build products, choose
Product > Archive. Xcode creates an archive of your project using the build configuration and name you
specified in the Archive pane of the scheme editor ("Create an Archive for Sharing or Submitting Your
Program" (page ?)) and saves the archive in the location specified in the Locations pane of Xcode preferences.


282


To see the archives for your project, open the archives organizer (Figure 11-10). You can add a comment by
clicking in the text field in the Comment column.
Figure
11-10

The archives organizer

For details on how to use archives to distribute your products, see "Distribute Your App" (page 284).


283

Distribute Your App

You distribute your app to share it with other persons in your development team, for user testing, or for
publication on the App Store.

Archive Your App
Before you can distribute your app, you have to archive it.
Archive your product for submission to iTunes Connect or for sharing with others. Schemes have an Archive
action with settings you use to customize the archive that Xcode creates when you choose Product > Archive.

To archive your app . . .
1.


2.

From the same menu, choose Edit Scheme to display the scheme dialog.

3.

In the left column, select Archive.

4.

Choose a build configuration.

5.

Specify a name for the archive and click OK.


284

Distribute Your App
Validate Your App

6.

Choose Product > Archive.

An archive is a bundle that includes your product along with symbol information. You can build an archive
to seed an application for testing or to validate and submit an application to iTunes Connect.
Your new archive appears in the Archives list in the Organizer window, unless you turn off this option. Each
archive is identified in the archives organizer with the date and time it was created. For more information,
see the related article on the archives organizer.
Important: If your app uses static libraries, you must ensure that those libraries are part of the app binary.
To learn how, see "Developing a Static Library and Incorporating It in Your App".

Validate Your App
Before distributing your app, you should validate the app archive to ensure that it passes essential iTunes
Connect tests.


285

Distribute Your App
Validate Your App

Validate your app to find out whether it meets minimum submission requirements.

To validate your app . . .
1.

In the Archives organizer, select the application archive you want to validate, and click Validate.

2.

For Mac distribution, select the distribution method, and click Next.

3.

Follow the instructions to complete the process.

Before submitting your app for publication on the App Store, you should validate it to ensure that it passes
standard iTunes Connect checks.
The screenshot shows the validation-method pane that appears for Mac distribution. This pane doesn’t
appear for iOS distribution.


286

Distribute Your App
Distribute Your iOS App

Troubleshooting: If Xcode doesn’t find an iTunes Connect application record for your application,
the dialog “No suitable application records were found” appears. This dialog also appears when
the application record state is not at least “Waiting for Upload”
.
●

Ensure that an application record exists for your application in iTunes Connect.

●

Ensure that the application record status is at least “Waiting to Upload.”

Distribute your iOS app to users or other members of your development team.

To distribute your iOS app . . .
1.

In the Archives organizer, select the application archive you want to distribute, and click Distribute.

2.

Select the distribution method, and click Next.


287

Distribute Your App

3.


Specifying the distribution method:
●

●

●

To submit the app for publication to the iOS App Store, select “Submit to the iOS App Store.”
To save a package of the app for enterprise or ad hoc (user testing) deployment, select “Save for
Enterprise or Ad-Hoc Deployment.”
To create an Xcode archive of the app to distribute to other members of your team, select “Export as
Xcode Archive.”

When using enterprise distribution, Xcode saves an enterprise-distribution manifest (as a property list file)
alongside the shared archive. For details about the contents of the enterprise-distribution manifest, see
developer.apple.com/programs/ios/enterprise.
If you saved a package or an Xcode archive of the app, send it to the people to whom you want to distribute
it.


288

Distribute Your App
Distribute Your Mac App

To learn more about distributing your iOS app, see "Distributing Apps".

Distribute your Mac app to users or other members of your development team.

To distribute your Mac app . . .
1.

In the Archives organizer, select the application archive you want to distribute, and click Distribute.

2.

Select the distribution method, and click Next.

3.


Here’s how you select the distribution method:
●

To submit the app for publication to the Mac App Store, select “Submit to the Mac App Store.”


289

Distribute Your App

●

To create an Xcode archive, an installation package, or a binary file of the app, select “Export as” and
choose the file format from the pop-up menu.

To learn more about distributing your Mac app, see "Submitting to the Mac App Store".


290

Document Revision History

This table describes the changes to Xcode 4 User Guide .
Date

Notes

2012-09-19

Made available in PDF.

2012-06-11

Added chapter about saving and reverting changes to files.
Added "Save and Revert Changes to Files" (page 244).

2011-10-12

Added features new in Xcode 4.2.

2011-08-10

Added features new in Xcode 4.1.
The following sections contain new information:
"Close a Project or a Workspace" (page 65); "Open a FIle Quickly" (page
130); "View Preprocessor or Assembly Output" (page 143); “Upgrade
Interface Builder Files That Use Plug-ins”; “Configure Sandboxing”;
"Customize Your Build and Run Workflow" (page ?); "Take a Snapshot
of Your Project" (page 252); "Save Internal Project Files in Repositories
" (page 278).

2011-05-07

Made editorial and format changes throughout.

2011-03-02

New document that explains how to use Xcode 4 to develop software for
iOS and OS X.


291

Apple Inc.
© 2012 Apple Inc.
All rights reserved.
No part of this publication may be reproduced,
stored in a retrieval system, or transmitted, in any
form or by any means, mechanical, electronic,
photocopying, recording, or otherwise, without
prior written permission of Apple Inc., with the
following exceptions: Any person is hereby
authorized to store documentation on a single
computer for personal use only and to print
copies of documentation for personal use
provided that the documentation contains
Apple’s copyright notice.
No licenses, express or implied, are granted with
respect to any of the technology described in this
document. Apple retains all intellectual property
rights associated with the technology described
in this document. This document is intended to
assist application developers to develop
applications only for Apple-labeled computers.
Apple Inc.
1 Infinite Loop
Cupertino, CA 95014
408-996-1010
Apple, the Apple logo, AppleScript, Cocoa, Cocoa
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iPod touch, iTunes, Leopard, Logic, Mac, Mac OS,
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