Rails console

15,558 views

Published on

Slides from a talk I gave about using the Ruby on Rails console (and irb) to develop Web applications. Describes the features of the console, and how you might want to use it.

1 Comment
15 Likes
Statistics
Notes
No Downloads
Views
Total views
15,558
On SlideShare
0
From Embeds
0
Number of Embeds
51
Actions
Shares
0
Downloads
111
Comments
1
Likes
15
Embeds 0
No embeds

No notes for slide
















































































  • Rails console

    1. 1. Using the Rails console Reuven M. Lerner reuven@lerner.co.il September 13th, 2010
    2. 2. Some basics • Ruby is interpreted • Last definition wins! • Runtime message sending (“method call”) decision-making • Open classes
    3. 3. The wrong way Write in IDE
    4. 4. The wrong way Write in Done? IDE
    5. 5. The wrong way Write in Done? Try in IDE browser
    6. 6. The wrong way It worked! Write in Done? Try in IDE browser
    7. 7. The wrong way It worked! Write in Done? Try in Failed? IDE browser
    8. 8. The wrong way It worked! Write in Done? Try in Failed? Use IDE browser debugger
    9. 9. The wrong way It worked! Write in Done? Try in Failed? Use IDE browser debugger Retry!
    10. 10. The Ruby way
    11. 11. The Ruby way Write in IDE Try in console
    12. 12. The Ruby way Write in Test IDE fails? Write a test Try in console
    13. 13. The Ruby way Write in Test IDE fails? Write a Done? Try in test browser Try in console
    14. 14. The Ruby way It worked! Write in Test IDE fails? Write a Done? Try in test browser Try in console
    15. 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. 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
    17. 17. 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)
    18. 18. Why use irb? • Test code • Debug code • Try things out • Better understand Ruby • Better understand an object or class
    19. 19. Rails requires more • development/test/production environments • ActiveRecord • Other libraries, such as ActiveSupport • HTTP requests and responses • Model and controller objects • Included gems
    20. 20. script/console • Wrapper around irb • Loads objects that are useful • Makes other objects easily available • Test your code, data, and assumptions
    21. 21. Invoking script/console • script/console • ruby scriptconsole (Windows version) • ruby script/console • script/console production
    22. 22. 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
    23. 23. Simple IRB stuff • Enter any Ruby code you want! • Result of evaluation is displayed on the screen
    24. 24. Examples >> 5 + 5 => 10 >> "foo".reverse => "oof" >> "foo".reverse.first => "o"
    25. 25. Printing vs. value >> puts "hello" hello => nil >> ['foo', 'bar', 'baz'].each do |word| ?> puts word >> end foo bar baz => ["foo", "bar", "baz"]
    26. 26. 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"]
    27. 27. 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"]
    28. 28. 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"]
    29. 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 This is what it prints bar baz => ["foo", "bar", "baz"] This is its value
    30. 30. 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
    31. 31. 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
    32. 32. 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
    33. 33. 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
    34. 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 Notice the prompt, showing line Returns nil numbers and block levels
    35. 35. Requiring files, gems >> require 'afile' >> gem 'afile'
    36. 36. 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
    37. 37. Variable assignment h = {:a => 1, :b => 2} a = [1, 2, 3, [h, h]] @p = Person.first @p = Person.all
    38. 38. Variable assignment h = {:a => 1, :b => 2} a = [1, 2, 3, [h, h]] @p = Person.first @p = Person.all Dynamic typing!
    39. 39. 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}]]
    40. 40. 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
    41. 41. Inspect with YAML puts @bob.to_yaml • Or: y @bob
    42. 42. 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
    43. 43. 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"]
    44. 44. 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"]
    45. 45. 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
    46. 46. 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
    47. 47. 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
    48. 48. 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 >>
    49. 49. Exiting from irb • Type “exit” • That’ll return you to the shell
    50. 50. 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
    51. 51. 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
    52. 52. Class methods Person.count Person.first Person.all Person.find(:all, :conditions => ["name like ? ", "%euve%"])
    53. 53. 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')
    54. 54. Huh? Named scopes? • Don’t worry — we’ll get to those in an upcoming session • They’re really great, though!
    55. 55. 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
    56. 56. 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
    57. 57. Experiment >> @p.update_attributes(:first_na me => 'Reuven') >> @george = Person.find_by_name('George') >> @bob = Person.find_by_name('Bob')
    58. 58. 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
    59. 59. 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
    60. 60. 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
    61. 61. 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!
    62. 62. 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"
    63. 63. 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>
    64. 64. The “app” object • Represents the Web application • Useful for: • Controllers • URLs • Routes
    65. 65. 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"
    66. 66. Submit requests >> app.get '/account/login' => 200 >> app.post '/account/login_action', {:email_address => 'reuven@lerner.co.il', :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"}
    67. 67. Handle redirects >> app.get '/' => 302 >> app.get_via_redirect '/' => 200 >> app.path => "/account/login"
    68. 68. 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
    69. 69. 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
    70. 70. .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
    71. 71. Naming .irbrc in Win32 • Name the file whatever you want • Set the environment variable IRBRC to point to that file • Done!
    72. 72. 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!
    73. 73. Configuration in Ruby! • IRB.conf is a hash • Set elements of this hash in .irbrc to change the configuration
    74. 74. 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
    75. 75. Autocomplete • Should be automatic (or :USE_READLINE) • Type TAB to complete things: >> abc = 5 => 5 >> abd = 6 => 6 >> ab[tab] abc abd abort
    76. 76. Emacs-style editing • Control-l • Control-p, Control-n • Control-a, Control-e • Control-b, Control-f • Control-d • Control-r for reverse search!
    77. 77. 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
    78. 78. 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")
    79. 79. ap — awesome_print gem install awesome_print >> h = {:a => [1,2,3], :b => 'hello'}
    80. 80. Nicely printed >> ap h { :b => "hello", :a => [ [0] 1, (Color not shown here) [1] 2, [2] 3 ] }
    81. 81. >> ap Person.last #<Person:0x7fd3acafcad0> { :id => 50877, :email_address => "foo@bar.wanadoo.co.uk", :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 }
    82. 82. wirble — color output! • gem install wirble • In your .irbrc: require 'wirble' Wirble.init Wirble.colorize
    83. 83. What returns X? require 'what_methods' >> 'abc'.what? 'a' "abc".first == "a" => ["first"]
    84. 84. 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
    85. 85. 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)
    86. 86. Contacting me • Call me in Israel: 054-496-8405 • Call me in the US: 847-230-9795 • E-mail me: reuven@lerner.co.il • Interrupt me: reuvenlerner (Skype/AIM)

    ×