C++ classes tutorials

Duhok Polytechnic UniversityDuhok Polytechnic University
Akre Technical InstituteAkre Technical Institute
IT DepartmentIT Department
Seminar AboutSeminar About
OOP COOP C##
Supervision:Supervision: Prepared By:Prepared By:
2014 -20152014 -2015
11

Object Oriented ProgrammingObject Oriented Programming
 ProgrammerProgrammer thinksthinks about and defines theabout and defines the
attributes and behavior of objects.attributes and behavior of objects.
 Often the objects are modeled after real-Often the objects are modeled after real-
world entities.world entities.
 Very different approach thanVery different approach than function-basedfunction-based
programming (like C).programming (like C).

Object Oriented ProgrammingObject Oriented Programming
 Object-oriented programming (OOP)Object-oriented programming (OOP)
– Encapsulates data (attributes) and functionsEncapsulates data (attributes) and functions
(behavior) into packages called classes.(behavior) into packages called classes.
 So, Classes are user-defined (programmer-So, Classes are user-defined (programmer-
defined) types.defined) types.
– Data (data members)Data (data members)
– Functions (member functions or methods)Functions (member functions or methods)
 In other words, they are structures +In other words, they are structures +
functionsfunctions

Reasons for OOPReasons for OOP
1.1. Simplify programmingSimplify programming
2.2. InterfacesInterfaces
 Information hiding:Information hiding:
– Implementation details hidden within classes themselvesImplementation details hidden within classes themselves
1.1. Software reuseSoftware reuse
 Class objects included as members of otherClass objects included as members of other
classesclasses

1- Access Modifiers (Access Specifiers)1- Access Modifiers (Access Specifiers)
describes as the scope of accessibility of an
Object and its members. All C# types and
type members have an accessibility level . We
can control the scope of the member object of
a class using access specifiers. We are using
access modifiers for providing security of our
applications. When we specify the
accessibility of a type or member we have to
declare it by using any of the access modifiers
provided by CSharp language.

public :
public is the most common access specifier in
C# . It can be access from anywhere, that
means there is no restriction on accessibility.
The scope of the accessibility is inside class
as well as outside. The type or member can
be accessed by any other code in the same
assembly or another assembly that
references it.
private :
The scope of the accessibility is limited only
inside the classes or struct in which they are

protected :
The scope of accessibility is limited within the
class or struct and the class derived (Inherited
)from this class.
internal :
The internal access modifiers can access
within the program that contain its
declarations and also access within the same
assembly level but not from another
assembly.
protected internal :
Protected internal is the same access levels

2- Constructors and
destructors
Constructors are special methods, used when
instantiating a class. A constructor can never
return anything, which is why you don't have
to define a return type for it. A normal method
is defined like this:
public string Describe()
A constructor can be defined like this:
public Car()
In our example for this chapter, we have a Car

{
}
public Car(string color)
{
this.color = color;
}
A constructor can call another constructor, which can come in
handy in several situations. Here is an example:
public Car()
{
Console.WriteLine("Constructor with no
parameters called!");
}
public Car(string color) : this()
{
this.color = color;
Console.WriteLine("Constructor with color
parameter called!");

If you run this code, you will see that the
constructor with no parameters is called first.
This can be used for instantiating various
objects for the class in the default constructor,
which can be called from other constructors
from the class. If the constructor you wish to
call takes parameters, you can do that as well.
Here is a simple example:

 public Car(string color) : this()
 {
 this.color = color;
 Console.WriteLine("Constructor with color
parameter called!");
 }

 public Car(string param1, string param2) :
this(param1)
 {

 }
 If you call the constructor which takes 2

DestructorsDestructors
Since C# is garbage collected, meaing that
the framework will free the objects that you no
longer use, there may be times where you
need to do some manual cleanup. A
destructor, a method called once an object is
disposed, can be used to cleanup resources
used by the object. Destructors doesn't look
very much like other methods in C#. Here is
an example of a destructor for our Car class:
~Car()

3-
C# - Copy Constructor in C# with Ex
 Introduction:
 Here I will explain what is copy constructor
in c# with example. Copy constructor in c#
is used to create new instance to the
values of an existing instance

 Description:
 In previous posts I explained
create captcha with refresh button in asp.net
,
use of virtual, override and new keyword with e
, method overloading and overriding,
delegates example in c#, sealed class in c#
, using statement in c#,
OOPS examples in c# and many articles
relating to interview questions in c#
, asp.net, SQL server, JavaScript, jQuery.
Now I will explain copy constructor

Copy Constructor
A parameterized constructor that contains a
parameter of same class type is called as
copy constructor. Main purpose of copy
constructor is to initialize new instance to the
values of an existing instance. Check below
example for this

using System;
namespace ConsoleApplication3
{
class Sample
{
public string param1, param2;
public Sample(string x, string y)
{
param1 = x;
param2 = y;
}
public Sample(Sample obj) // Copy

4-Friend Functions
A friend function is a function that is not a
member of a class but has access to the
class's private and protected members. Friend
functions are not considered class members;
they are normal external functions that are
given special access privileges. Friends are
not in the class's scope, and they are not
called using the member-selection operators
(.and –>) unless they are members of another
class. A friend function is declared by the

Example
// friend_functions.cpp
// compile with: /EHsc
#include <iostream>

using namespace std;
class Point
{
friend void ChangePrivate( Point & );
public:
Point( void ) : m_i(0) {}

1919
ReferenceReference
 R. C. Gonzolez, R. E. Woods, "Digital Image Processing R. C. Gonzolez, R. E. Woods, "Digital Image Processing
second edition", Prentice Hall, 2002.second edition", Prentice Hall, 2002.
 R. C. Gonzolez, R. E. Woods, S. L. Eddins, "Digital R. C. Gonzolez, R. E. Woods, S. L. Eddins, "Digital
Image Processing Using Matlab", Prentice Hall, 2004.Image Processing Using Matlab", Prentice Hall, 2004.
 T. Acharya, A. K. Ray, "Image Processing: Principles and T. Acharya, A. K. Ray, "Image Processing: Principles and
Applications", John Wiley & Sons, 2005.Applications", John Wiley & Sons, 2005.
 B. E. Usevitch, 'A Tutorial on Modern Lossy Wavelet B. E. Usevitch, 'A Tutorial on Modern Lossy Wavelet
Image Compression: Foundations of JPEG 2000', IEEE Image Compression: Foundations of JPEG 2000', IEEE
Signal Processing Magazine, vol. 18, pp. 22-35, Sept. Signal Processing Magazine, vol. 18, pp. 22-35, Sept.
2001. 2001.

C++ classes tutorials

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