Rails console

Using the Rails console Reuven M. Lerner reuven@lerner.co.il September 13th, 2010

Some basics • Ruby is interpreted • Last deﬁnition wins! • Runtime message sending (“method call”) decision-making • Open classes

The wrong way Write in IDE

The wrong way Write in Done? IDE

The wrong way Write in Done? Try in IDE browser

The wrong way It worked! Write in Done? Try in IDE browser

The wrong way It worked! Write in Done? Try in Failed? IDE browser

The wrong way It worked! Write in Done? Try in Failed? Use IDE browser debugger

The wrong way It worked! Write in Done? Try in Failed? Use IDE browser debugger Retry!

The Ruby way

The Ruby way Write in IDE Try in console

The Ruby way Write in Test IDE fails? Write a test Try in console

The Ruby way Write in Test IDE fails? Write a Done? Try in test browser Try in console

The Ruby way It worked! Write in Test IDE fails? Write a Done? Try in test browser Try in console

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

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

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)

Why use irb? • Test code • Debug code • Try things out • Better understand Ruby • Better understand an object or class

Rails requires more • development/test/production environments • ActiveRecord • Other libraries, such as ActiveSupport • HTTP requests and responses • Model and controller objects • Included gems

script/console • Wrapper around irb • Loads objects that are useful • Makes other objects easily available • Test your code, data, and assumptions

Invoking script/console • script/console • ruby scriptconsole (Windows version) • ruby script/console • script/console production

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

Simple IRB stuff • Enter any Ruby code you want! • Result of evaluation is displayed on the screen

Examples >> 5 + 5 => 10 >> "foo".reverse => "oof" >> "foo".reverse.first => "o"

Printing vs. value >> puts "hello" hello => nil >> ['foo', 'bar', 'baz'].each do |word| ?> puts word >> end foo bar baz => ["foo", "bar", "baz"]

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"]

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"]

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"]

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

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

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

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

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

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

Requiring ﬁles, gems >> require 'afile' >> gem 'afile'

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

Variable assignment h = {:a => 1, :b => 2} a = [1, 2, 3, [h, h]] @p = Person.first @p = Person.all

Variable assignment h = {:a => 1, :b => 2} a = [1, 2, 3, [h, h]] @p = Person.first @p = Person.all Dynamic typing!

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}]]

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

Inspect with YAML puts @bob.to_yaml • Or: y @bob

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

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"]

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"]

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

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

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

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 >>

Exiting from irb • Type “exit” • That’ll return you to the shell

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

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

Class methods Person.count Person.first Person.all Person.find(:all, :conditions => ["name like ? ", "%euve%"])

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')

Huh? Named scopes? • Don’t worry — we’ll get to those in an upcoming session • They’re really great, though!

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

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

Experiment >> @p.update_attributes(:first_na me => 'Reuven') >> @george = Person.find_by_name('George') >> @bob = Person.find_by_name('Bob')

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

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

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

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!

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"

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>

The “app” object • Represents the Web application • Useful for: • Controllers • URLs • Routes

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"

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"}

Handle redirects >> app.get '/' => 302 >> app.get_via_redirect '/' => 200 >> app.path => "/account/login"

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

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

.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

Naming .irbrc in Win32 • Name the ﬁle whatever you want • Set the environment variable IRBRC to point to that ﬁle • Done!

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!

Conﬁguration in Ruby! • IRB.conf is a hash • Set elements of this hash in .irbrc to change the conﬁguration

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

Autocomplete • Should be automatic (or :USE_READLINE) • Type TAB to complete things: >> abc = 5 => 5 >> abd = 6 => 6 >> ab[tab] abc abd abort

Emacs-style editing • Control-l • Control-p, Control-n • Control-a, Control-e • Control-b, Control-f • Control-d • Control-r for reverse search!

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

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")

ap — awesome_print gem install awesome_print >> h = {:a => [1,2,3], :b => 'hello'}

Nicely printed >> ap h { :b => "hello", :a => [ [0] 1, (Color not shown here) [1] 2, [2] 3 ] }

>> 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 }

wirble — color output! • gem install wirble • In your .irbrc: require 'wirble' Wirble.init Wirble.colorize

What returns X? require 'what_methods' >> 'abc'.what? 'a' "abc".first == "a" => ["first"]

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

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)

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)

Rails console

by Reuven Lerner on Sep 14, 2010

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Rails console — Presentation Transcript