Rails console
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The document is a comprehensive guide on using the Rails console for Ruby programming, covering fundamentals, interactive Ruby (IRB) usage, and specific approaches to testing and debugging code. It emphasizes the importance of the console in understanding Ruby better, testing objects, and experimenting with code in a safe environment. Additionally, it provides practical examples and tips for efficient use of features like variable assignment, inspecting objects, ActiveRecord methods, and Rails helpers.
![Printing vs. value
>> puts "hello"
hello
=> nil
>> ['foo', 'bar', 'baz'].each do |word|
?> puts word
>> end
foo
bar
baz
=> ["foo", "bar", "baz"]](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-27-320.jpg)
![Printing vs. value
>> puts "hello" This is what it prints
hello
=> nil
>> ['foo', 'bar', 'baz'].each do |word|
?> puts word
>> end
foo
bar
baz
=> ["foo", "bar", "baz"]](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-28-320.jpg)
![Printing vs. value
>> puts "hello" This is what it prints
hello
=> nil This is its value
>> ['foo', 'bar', 'baz'].each do |word|
?> puts word
>> end
foo
bar
baz
=> ["foo", "bar", "baz"]](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-29-320.jpg)
![Printing vs. value
>> puts "hello" This is what it prints
hello
=> nil This is its value
>> ['foo', 'bar', 'baz'].each do |word|
?> puts word
>> end
foo This is what it prints
bar
baz
=> ["foo", "bar", "baz"]](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-30-320.jpg)
![Printing vs. value
>> puts "hello" This is what it prints
hello
=> nil This is its value
>> ['foo', 'bar', 'baz'].each do |word|
?> puts word
>> end
foo This is what it prints
bar
baz
=> ["foo", "bar", "baz"]
This is its value](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-31-320.jpg)
![Variable assignment
h = {:a => 1, :b => 2}
a = [1, 2, 3, [h, h]]
@p = Person.first
@p = Person.all](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-39-320.jpg)
![Variable assignment
h = {:a => 1, :b => 2}
a = [1, 2, 3, [h, h]]
@p = Person.first
@p = Person.all Dynamic typing!](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-40-320.jpg)
![Viewing variables
>> a
=> [1, 2, 3, [{:b=>2, :a=>1}, {:b=>2, :a=>1}]]
>> h[:c] = 3
=> 3
>> a
=> [1, 2, 3, [{:b=>2, :a=>1, :c=>3},
{:b=>2, :a=>1, :c=>3}]]](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-41-320.jpg)
![Defining classes
>> class Train
>> attr :passengers
>> def initialize
>> @passengers = [ ]
>> end
>> end
=> nil
>> t = Train.new
=> #<Train:0x102f391e0 @passengers=[]>
>> t.passengers << 'Reuven'
=> ["Reuven"]
>> t.passengers << 'Atara'
=> ["Reuven", "Atara"]](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-45-320.jpg)
![Defining classes
>> class Train
>> attr :passengers
>> def initialize
>> @passengers = [ ]
>> end
>> end Class definitions evaluate to nil
=> nil
>> t = Train.new
=> #<Train:0x102f391e0 @passengers=[]>
>> t.passengers << 'Reuven'
=> ["Reuven"]
>> t.passengers << 'Atara'
=> ["Reuven", "Atara"]](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-46-320.jpg)
![Made a mistake?
• Use control-c to return to the top level
>> ['foo','bar','bat'].each do |word|
?> [1,2,3].each do |num|
?> ^C
>>](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-50-320.jpg)
![Class methods
Person.count
Person.first
Person.all
Person.find(:all, :conditions
=> ["name like ? ", "%euve%"])](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-54-320.jpg)
![Named scopes
• If you have a named scope:
named_scope :created_since, lambda
{ |since| { :conditions =>
['created_at >= ? ', since] }}
• Then it’s available as a class method, and we
can run it from inside of the console
>> Node.created_since('2010-9-1')](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-55-320.jpg)
![Look at the response
>> app.get '/account/login'
=> 200
>> app.response.response_code
=> 200
>> app.response.body[0..100]
=> "<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Transitional//EN"n "http://www.w3.org/TR/
xhtml1"
>> app.response.has_flash?
=> false](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-71-320.jpg)
![AUTO_INDENT
IRB.conf[:AUTO_INDENT]=true
• When you start a block, the prompt indents
you a little bit
• It’s not super-smart, but better than nothing](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-77-320.jpg)
![Autocomplete
• Should be automatic (or :USE_READLINE)
• Type TAB to complete things:
>> abc = 5
=> 5
>> abd = 6
=> 6
>> ab[tab]
abc abd abort](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-78-320.jpg)
![Save history
require 'irb/ext/save-history'
IRB.conf[:USE_READLINE] = true
IRB.conf[:SAVE_HISTORY] = 1000
IRB.conf[:HISTORY_PATH] =
File::expand_path("~/.irb.hist
ory")](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-81-320.jpg)
![ap — awesome_print
gem install awesome_print
>> h = {:a => [1,2,3], :b =>
'hello'}](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-82-320.jpg)
![Nicely printed
>> ap h
{
:b => "hello",
:a => [
[0] 1, (Color not shown here)
[1] 2,
[2] 3
]
}](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-83-320.jpg)
![What returns X?
require 'what_methods'
>> 'abc'.what? 'a'
"abc".first == "a"
=> ["first"]](https://image.slidesharecdn.com/railsconsole-100914011835-phpapp02/85/Rails-console-86-320.jpg)
Rails console
- 1. Using the Rails console Reuven M. Lerner [email protected] September 13th, 2010
- 2. Some basics • Ruby is interpreted • Last definition wins! • Runtime message sending (“method call”) decision-making • Open classes
- 3. The wrong way Write in IDE
- 4. The wrong way Write in Done? IDE
- 5. The wrong way Write in Done? Try in IDE browser
- 6. The wrong way It worked! Write in Done? Try in IDE browser
- 7. The wrong way It worked! Write in Done? Try in Failed? IDE browser
- 8. The wrong way It worked! Write in Done? Try in Failed? Use IDE browser debugger
- 9. The wrong way It worked! Write in Done? Try in Failed? Use IDE browser debugger Retry!
- 10. The Ruby way
- 11. The Ruby way Write in IDE Try in console
- 12. The Ruby way Write in Test IDE fails? Write a test Try in console
- 13. The Ruby way Write in Test IDE fails? Write a Done? Try in test browser Try in console
- 14. The Ruby way It worked! Write in Test IDE fails? Write a Done? Try in test browser Try in console
- 15. The Ruby way Read logs, backtrace It worked! Write in Test IDE fails? Write a Done? Try in Failed? Try in test browser console Try in console Debugger
- 16. Whoa, that’s a lot! • The idea is that the code is an extension of your thoughts • By “swimming through” and “playing with” the code, you understand it better, and can work with it faster
- 19. irb • Interactive Ruby! (Comes with Ruby) • Fire it up, and type Ruby code • Define variables, classes, modules, methods • All definitions disappear when you exit • (Except for persistent storage, of course)
- 20. Why use irb? • Test code • Debug code • Try things out • Better understand Ruby • Better understand an object or class
- 21. Rails requires more • development/test/production environments • ActiveRecord • Other libraries, such as ActiveSupport • HTTP requests and responses • Model and controller objects • Included gems
- 22. script/console • Wrapper around irb • Loads objects that are useful • Makes other objects easily available • Test your code, data, and assumptions
- 23. Invoking script/console • script/console • ruby scriptconsole (Windows version) • ruby script/console • script/console production
- 24. When? • Always. • It’s very rare for me to work on a Rails project without a console open • The console is where I test my objects, experiment with code that’s longer than one line, and try to debug my code
- 25. Simple IRB stuff • Enter any Ruby code you want! • Result of evaluation is displayed on the screen
- 26. Examples >> 5 + 5 => 10 >> "foo".reverse => "oof" >> "foo".reverse.first => "o"
- 27. Printing vs. value >> puts "hello" hello => nil >> ['foo', 'bar', 'baz'].each do |word| ?> puts word >> end foo bar baz => ["foo", "bar", "baz"]
- 28. Printing vs. value >> puts "hello" This is what it prints hello => nil >> ['foo', 'bar', 'baz'].each do |word| ?> puts word >> end foo bar baz => ["foo", "bar", "baz"]
- 29. Printing vs. value >> puts "hello" This is what it prints hello => nil This is its value >> ['foo', 'bar', 'baz'].each do |word| ?> puts word >> end foo bar baz => ["foo", "bar", "baz"]
- 30. Printing vs. value >> puts "hello" This is what it prints hello => nil This is its value >> ['foo', 'bar', 'baz'].each do |word| ?> puts word >> end foo This is what it prints bar baz => ["foo", "bar", "baz"]
- 31. Printing vs. value >> puts "hello" This is what it prints hello => nil This is its value >> ['foo', 'bar', 'baz'].each do |word| ?> puts word >> end foo This is what it prints bar baz => ["foo", "bar", "baz"] This is its value
- 32. Multi-line irb irb(main):001:0> class Blah irb(main):002:1> def sayit irb(main):003:2> puts "hi" irb(main):004:2> end irb(main):005:1> end => nil
- 33. Multi-line irb Open a class irb(main):001:0> class Blah irb(main):002:1> def sayit irb(main):003:2> puts "hi" irb(main):004:2> end irb(main):005:1> end => nil
- 34. Multi-line irb Open a class irb(main):001:0> class Blah irb(main):002:1> def sayit (Re)define a method irb(main):003:2> puts "hi" irb(main):004:2> end irb(main):005:1> end => nil
- 35. Multi-line irb Open a class irb(main):001:0> class Blah irb(main):002:1> def sayit (Re)define a method irb(main):003:2> puts "hi" irb(main):004:2> end irb(main):005:1> end => nil Notice the prompt, showing line numbers and block levels
- 36. Multi-line irb Open a class irb(main):001:0> class Blah irb(main):002:1> def sayit (Re)define a method irb(main):003:2> puts "hi" irb(main):004:2> end irb(main):005:1> end => nil Notice the prompt, showing line Returns nil numbers and block levels
- 37. Requiring files, gems >> require 'afile' >> gem 'afile'
- 38. Variable assignment • It works perfectly! • Local, instance variables both work — but instance variables don’t buy you anything • Except namespace conflict avoidance • Assignments disappear when irb exits
- 39. Variable assignment h = {:a => 1, :b => 2} a = [1, 2, 3, [h, h]] @p = Person.first @p = Person.all
- 40. Variable assignment h = {:a => 1, :b => 2} a = [1, 2, 3, [h, h]] @p = Person.first @p = Person.all Dynamic typing!
- 41. Viewing variables >> a => [1, 2, 3, [{:b=>2, :a=>1}, {:b=>2, :a=>1}]] >> h[:c] = 3 => 3 >> a => [1, 2, 3, [{:b=>2, :a=>1, :c=>3}, {:b=>2, :a=>1, :c=>3}]]
- 42. Inspecting objects • Just type the object’s name >> @bob => #<User:0x2645874 @new_record=true, @attributes={"name"=>"Bob", "job"=>"Test Dummy"}> • notice instance variables and attributes
- 43. Inspect with YAML puts @bob.to_yaml • Or: y @bob
- 44. Classes, modules, and methods • You can define any or all of these • Definitions work, and stick around for the duration of the irb session • Invisible to your running application • When you exit, the definitions disappear
- 45. Defining classes >> class Train >> attr :passengers >> def initialize >> @passengers = [ ] >> end >> end => nil >> t = Train.new => #<Train:0x102f391e0 @passengers=[]> >> t.passengers << 'Reuven' => ["Reuven"] >> t.passengers << 'Atara' => ["Reuven", "Atara"]
- 46. Defining classes >> class Train >> attr :passengers >> def initialize >> @passengers = [ ] >> end >> end Class definitions evaluate to nil => nil >> t = Train.new => #<Train:0x102f391e0 @passengers=[]> >> t.passengers << 'Reuven' => ["Reuven"] >> t.passengers << 'Atara' => ["Reuven", "Atara"]
- 47. Define a new ActiveRecord class >> class Blah < ActiveRecord::Base >> end => nil >> Blah.first ActiveRecord::StatementInvalid: RuntimeError: ERROR C42P01 Mrelation "blahs" does not exist P15 Fparse_relation.c L857 RparserOpenTable: SELECT * FROM "blahs" LIMIT 1
- 48. Define a new ActiveRecord class >> class Blah < ActiveRecord::Base >> end => nil Runtime message binding >> Blah.first ActiveRecord::StatementInvalid: RuntimeError: ERROR C42P01 Mrelation "blahs" does not exist P15 Fparse_relation.c L857 RparserOpenTable: SELECT * FROM "blahs" LIMIT 1
- 49. Avoiding huge output • Person.all will return many records — and thus print many records • Assignment returns the assigned value • Put a “;nil” after your command, and it’ll evaluate to null, without any output! •@people = Person.all; nil
- 50. Made a mistake? • Use control-c to return to the top level >> ['foo','bar','bat'].each do |word| ?> [1,2,3].each do |num| ?> ^C >>
- 51. Exiting from irb • Type “exit” • That’ll return you to the shell
- 52. ActiveRecord • ActiveRecord classes are available • Console talks to the database for the current environment • Type the name of a class to see its fields • Use class methods • Create instances, use instance methods
- 53. ActiveRecord fields >> Person => Personid: integer, email_address: string, first_name: string, last_name: string, password: string, administrator: boolean, created_at: datetime, updated_at: datetime, avatar_file_name: text, avatar_content_type: string, avatar_file_size: integer, avatar_updated_at: datetime
- 54. Class methods Person.count Person.first Person.all Person.find(:all, :conditions => ["name like ? ", "%euve%"])
- 55. Named scopes • If you have a named scope: named_scope :created_since, lambda { |since| { :conditions => ['created_at >= ? ', since] }} • Then it’s available as a class method, and we can run it from inside of the console >> Node.created_since('2010-9-1')
- 56. Huh? Named scopes? • Don’t worry — we’ll get to those in an upcoming session • They’re really great, though!
- 57. Testing validity >> @p = Person.new => #<Person id: nil, email_address: nil, first_name: nil, last_name: nil, password: nil, administrator: nil, created_at: nil, updated_at: nil, avatar_file_name: nil, avatar_content_type: nil, avatar_file_size: nil, avatar_updated_at: nil> >> @p.valid? => false
- 58. Method differences >> @p.save => false >> @p.save! ActiveRecord::RecordInvalid: Validation failed: First name can't be blank, Last name can't be blank, Email address can't be blank, Email address - Invalid email address, Password can't be blank
- 59. Experiment >> @p.update_attributes(:first_na me => 'Reuven') >> @george = Person.find_by_name('George') >> @bob = Person.find_by_name('Bob')
- 60. Reloading reload! • Do this every time you change a model • You will probably have to re-create instances of ActiveRecord objects • Otherwise, odd things can happen
- 61. Fat models = easier testing • ActiveRecord methods are immediately available in the console • This means that you can test your code more easily when it’s in ActiveRecord • Fat models win again! • Remember: Keep your controllers skinny
- 63. Sandbox • script/console production --sandbox • Reverts all changes that you made to the database • Allows you to work on your production database without having to worry that you’ll destroy things
- 64. Helpers • Helpers: Methods for use within views • Available under the “helper” object • There are lots of helpers, and they have lots of options. Test them before they’re in your views!
- 65. Helper examples >> helper.number_to_currency(123.45) => "$123.5" >> helper.number_to_currency(123.45, :precision => 1) => "$123.5" >> helper.pluralize(2, 'person') => "2 people" >> helper.pluralize(2, 'knife') => "2 knives"
- 66. Who defined a helper? >> helper.method(:add_tag_link) => #<Method: ActionView::Base(ApplicationHelper)#add_tag_link> >> helper.method(:truncate) => #<Method: ActionView::Base(ActionView::Helpers::TextHelper)#tru ncate> >> helper.method(:number_to_currency) => #<Method: ActionView::Base(ActionView::Helpers::NumberHelper)#n umber_to_currency>
- 67. The “app” object • Represents the Web application • Useful for: • Controllers • URLs • Routes
- 68. What URL? >> app.url_for(:controller => :account) => "http://www.example.com/account" >> app.url_for(:controller => :account, :action => :login) => "http://www.example.com/account/ login"
- 69. Submit requests >> app.get '/account/login' => 200 >> app.post '/account/login_action', {:email_address => '[email protected]', :password => 'password'} => 200 >> app.session => {"flash"=>{:notice=>"Sorry, but no user exists with that e-mail address and password. Please try again."}} >> app.cookies => {"_nlcommons_session"=>"4bd4fb842ef5f5dfdc4c09fc05e0c a2c"}
- 70. Handle redirects >> app.get '/' => 302 >> app.get_via_redirect '/' => 200 >> app.path => "/account/login"
- 71. Look at the response >> app.get '/account/login' => 200 >> app.response.response_code => 200 >> app.response.body[0..100] => "<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"n "http://www.w3.org/TR/ xhtml1" >> app.response.has_flash? => false
- 72. ri • Get documentation from within irb/console: >> ri 'String#new' >> ri 'String#length' • Works really nicely, but it can take a long time to execute
- 73. .irbrc • Code is executed every time you run IRB or console • If a line causes trouble, it silently fails and stops reading the file • Yes, this is really dumb • Great for loading files, configuration settings
- 74. Naming .irbrc in Win32 • Name the file whatever you want • Set the environment variable IRBRC to point to that file • Done!
- 75. IRB configuration • IRB (and the console) is an essential tool • There are many configuration parameters and gems you can use to enhance it • They’re great!
- 76. Configuration in Ruby! • IRB.conf is a hash • Set elements of this hash in .irbrc to change the configuration
- 77. AUTO_INDENT IRB.conf[:AUTO_INDENT]=true • When you start a block, the prompt indents you a little bit • It’s not super-smart, but better than nothing
- 78. Autocomplete • Should be automatic (or :USE_READLINE) • Type TAB to complete things: >> abc = 5 => 5 >> abd = 6 => 6 >> ab[tab] abc abd abort
- 79. Emacs-style editing • Control-l • Control-p, Control-n • Control-a, Control-e • Control-b, Control-f • Control-d • Control-r for reverse search!
- 80. Emacs-style editing • Control-l • Control-p, Control-n • Control-a, Control-e • Control-b, Control-f • Control-d • Control-r for reverse search! My favorite
- 81. Save history require 'irb/ext/save-history' IRB.conf[:USE_READLINE] = true IRB.conf[:SAVE_HISTORY] = 1000 IRB.conf[:HISTORY_PATH] = File::expand_path("~/.irb.hist ory")
- 82. ap — awesome_print gem install awesome_print >> h = {:a => [1,2,3], :b => 'hello'}
- 83. Nicely printed >> ap h { :b => "hello", :a => [ [0] 1, (Color not shown here) [1] 2, [2] 3 ] }
- 84. >> ap Person.last #<Person:0x7fd3acafcad0> { :id => 50877, :email_address => "[email protected]", :encrypted_password => "stanman42", :first_name => "Foo", :last_name => "Barman", :address => "3 Foo Way", :city => "Congleton", :state_id => 1, :zip_code => "CW12 1LU", :phone_number => "01260 999999", :payment_method_id => 2, :notes => nil, :receive_mailings_p => false, :admin_p => false, :deleted_p => false, :heard_of_us_via => nil, :agree_to_policy_p => true, :monthly_payment_limit => 300, :monthly_book_limit => 50, :visitor_source_id => nil, :link_admin_p => false }
- 85. wirble — color output! • gem install wirble • In your .irbrc: require 'wirble' Wirble.init Wirble.colorize
- 86. What returns X? require 'what_methods' >> 'abc'.what? 'a' "abc".first == "a" => ["first"]
- 87. Summary • Use the console! • The more you use the console, the more comfortable you’ll feel with Ruby • It will save you lots of time and effort
- 88. Inspiration • Amy Hoy’s “slash7” blog (http://slash7.com/ 2006/12/21/secrets-of-the-rails-console- ninjas/) • “Err the blog” posting “IRB mix tape” (http:// errtheblog.com/posts/24-irb-mix-tape) • StackOverflow posting on “favorite IRB tricks” (http://stackoverflow.com/questions/ 123494/whats-your-favourite-irb-trick)
- 89. Contacting me • Call me in Israel: 054-496-8405 • Call me in the US: 847-230-9795 • E-mail me: [email protected] • Interrupt me: reuvenlerner (Skype/AIM)