Learning Ruby's Dynamism with Rails

* Class-exp with AR
* include and extend with AS::Concern
* Standard Callbacks

Transcript

1. Learning Ruby's Dynamism with Rails @wtnabe Kanazawa.rb meetup #15 2013-11-23 (Sat) at IT Plaza Musashi
2. Topics
3. Class-exp with AR include and extend with AS::Concern Standard Callbacks
4. Class-exp with ActiveRecord
5. ActiveRecord example class Book < ActiveRecord::Base belongs_to :bookstand validates :name, :presence => true scope :done, -> {where(:done => true)} def recent? published_at >= 1.year.ago end end
6. ActiveRecord Pattern Class has table and ER definition Instance has DB record and relative methods
7. Just another OOPL class Book extends ActiveRecord\Model { static $belongs_to = array( array('bookstand') ); static $validates_presence_of = array( array('name') ); public static function done() {} public function is_recent() {} }
8. class Book < ActiveRecord::Base belongs_to :bookstand validates :name, :presence => true scope :done, -> {where(:done => true)} def recent? published_at >= 1.year.ago end end
9. class Book < ActiveRecord::Base # class method call belongs_to :bookstand # class method call validates :name, :presence => true # class method call scope :done, -> {where(:done => true)} # instance method definition def recent? published_at >= 1.year.ago end end
10. Ruby's Class Class is expression class keyword changes context It runs all class methods callable in class context
11. include and extend with ActiveSupport::Concern
12. new Rails 4 app. app ├── assets │ ├── images │ ├── javascripts │ └── stylesheets ├── controllers │ └── concerns <-- what ? ├── helpers ├── mailers ├── models │ └── concerns <-- what ? └── views └── layouts
13. ActiveSupport::Concern Actually added from ActiveSupport 3.0
14. What does it do ? include & extend
15. include module ModA def methodA; p 'methodA'; end end class KlassA include ModA end KlassA.new.methodA # => "methodA"
16. extend module ModB def methodB; p 'methodB'; end end class KlassB extend ModB end KlassB.methodB # => "methodB"
17. Concern module M extend ActiveSupport::Concern included do scope :foo, :conditions => {:created_at => nil} end module ClassMethods def cm; puts 'I am a class method'; end end module InstanceMethods def im; puts 'I am an instance method'; end end end
18. When to use class ModelA < ActiveRecord::Base include M end class ModelB < ActiveRecord::Base include M end treat common attributes with multi-models
19. ActiveRecord call class methods define class methods define instance methods
20. class Book < ActiveRecord::Base # call class methods belongs_to :bookstand validates :name, :presence => true scope :done, -> {where(:done => true)} # define class methods class << self def recent self.where(:published_ad >= 1.year.ago) end end # define instance methods def recent? published_at >= 1.year.ago end end
21. ActiveSupport::Concern module M included do # call class methods end module ClassMethods ... end module InstanceMethods ... end end
22. AS::Concern is a AR's best friend cf. https://www.ruby-lang.org/
23. Standard Callbacks
24. Rails Callback Examples before_validation after_save before_action ( before_filter ) called Filter, but Callback internally
25. How to use class Controller < ApplicationController before_action :auth, :unless => :logged_in? end class Model < ActiveRecord::Base before_validation do normalize_attributes end end ※ :unless keyword is allowed from ActiveSupport::Callbacks 4.0
26. Ruby has many Callbacks
27. Module.private_methods.sort.grep(/ed\z/) # => [:inherited, :included, :extended, :prepended, :method_added, :method_removed, :method_undefined, :protected, :singleton_method_added, :singleton_method_removed, :singleton_method_undefined]
28. Object#initialize, Object#method_messing, Module#append_features, ... append_features is called before execute include
29. ex1) extended module M extend ActiveSupport::Concern end module ActiveSupport module Concern def self.extended(base) ... end end end
30. ex2) inherited class Klass def self.inherited(name) raise StandardError, "#{name} cannot inherit #{self}" end end
31. Similar to Final keyword class Subklass < Klass; end # => ...:3:in `inherited': # Subklass cannot inherit Klass (StandardE
32. Conclusion
33. Ruby is Dynamic ! Class is expression Class can be modified easily with AS::Concern Useful Standard Callbacks
34. Rails uses Ruby's dynamism very well
35. Enjoy Rails & Ruby !