ActiveRecord Associations (2), Season 1

1. The 8th Round of ROR Lab. Active Record Associations - 2 March 3rd, 2012 Hyoseong Choi ROR Lab.

2. Short Review ROR Lab.

3. For what? Primary & Foreign Keys customer order id id ROR Lab.

4. For what? Primary & Foreign Keys customer order id id customer_id parent obj. child obj. ROR Lab.

5. For what? Primary & Foreign Keys customer order id id Active Record customer_id Assocation parent obj. child obj. ROR Lab.

6. For what? ROR Lab.

7. For what? To add an order ROR Lab.

8. For what? To add an order ROR Lab.

9. For what? To add an order To delete a customer ROR Lab.

10. For what? To add an order To delete a customer ROR Lab.

11. Associations Parent Class Child Class has_one 1 :1 belongs_to has_one, :through 1 :n has_many belongs_to has_many A has_many B, :through belongs_to n :m has_many B has_many A, :through has_and_belongs_to_many ROR Lab.

12. Association Options belongs_to options has_one options has_many options HABTM options • :autosave • :as • :as • :association_foreign_key • :class_name • :autosave • :autosave • :autosave • :conditions • :class_name • :class_name • :class_name • :counter_cache • :conditions • :conditions • :conditions • :dependent • :dependent • :counter_sql • :counter_sql • :foreign_key • :foreign_key • :dependent • :delete_sql • :include • :include • :extend • :extend • :polymorphic • :order • :finder_sql • :finder_sql • :readonly • :primary_key • :foreign_key • :foreign_key • :select • :readonly • :group • :group • :touch • :select • :include • :include • :validate • :source • :limit • :insert_sql • :source_type • :offset • :join_table • :through • :order • :limit • :validate • :primary_key • :offset • :readonly • :order • :select • :readonly • :source • :select • :source_type • :uniq • :through • :validate • :uniq • :validate ROR Lab.

13. Polymorphic Imageable Picture id imageable_id Imageable Picture id imageable_id ROR Lab.

14. Polymorphic Imageable Picture Employee id id imageable_id Imageable Picture Product id id imageable_id ROR Lab.

15. :counter_cache • But, you should add “orders_count” column to Customer model • You can override the default column name. • ReadOnly !!! ROR Lab.

16. :counter_cache • But, you should add “orders_count” column to Customer model • You can override the default column name. • ReadOnly !!! ROR Lab.

17. :touch ROR Lab.

18. :touch ROR Lab.

19. :touch Or using a custom attribute ROR Lab.

20. :touch Or using a custom attribute ROR Lab.

21. ActiveRecord Association - 2 ROR Lab.

22. Association Options belongs_to options has_one options has_many options HABTM options • :autosave • :autosave • :autosave • :autosave • :class_name • :class_name • :class_name • :class_name • :conditions • :conditions • :conditions • :conditions • :foreign_key • :foreign_key • :foreign_key • :foreign_key • :include • :include • :include • :include • :readonly • :readonly • :readonly • :readonly • :select • :select • :select • :select • :validate • :validate • :validate • :validate • :dependent • :as • :as • :order • :counter_cache • :order • :order • :counter_sql • :polymorphic • :primary_key • :primary_key • :extend • :touch • :source • :source • :finder_sql • :source_type • :source_type • :group • :through • :through • :limit • :dependent • :counter_sql • :offset • :extend • :uniq • :finder_sql • :association_foreign_key • :group • :delete_sql • :limit • :insert_sql • :offset • :join_table • :uniq • :dependent ROR Lab.

30. Common Options • :autosave • :class_name • :conditions • :foreign_key • :include • :readonly • :select • :validate ROR Lab.

31. - common options - :autosave • No declaration (default) : new children are saved when their parent is saved • :autosave => true : all children is saved, no matter whether they are new records • :autosave => false : any children is not saved ROR Lab.

32. - common options - :autosave class Post has_one :author, :autosave => true end has_one post = Post.find(1) post.title # => "The current global position of migrating ducks" post.author.name # => "alloy" post.title = "On the migration of ducks" post.author.name = "Eloy Duran" post.save post.reload post.title # => "On the migration of ducks" post.author.name # => "Eloy Duran" post.author.mark_for_destruction post.author.marked_for_destruction? # => true id = post.author.id Author.find_by_id(id).nil? # => false post.save post.reload.author # => nil Author.find_by_id(id).nil? # => true http://api.rubyonrails.org/classes/ActiveRecord/AutosaveAssociation.html ROR Lab.

33. - common options - :autosave has_many class Post has_many :comments # :autosave option is no declared end post = Post.new(:title => 'ruby rocks') post.comments.build(:body => 'hello world') post.save # => saves both post and comment post = Post.create(:title => 'ruby rocks') post.comments.build(:body => 'hello world') post.save # => saves both post and comment post = Post.create(:title => 'ruby rocks') post.comments.create(:body => 'hello world') post.save # => saves both post and comment class Post has_many :comments, :autosave => true end post = Post.create(:title => 'ruby rocks') post.comments.create(:body => 'hello world') post.comments[0].body = 'hi everyone' post.save # => saves both post and comment, with 'hi everyone' as body post.comments.last.mark_for_destruction post.comments.last.marked_for_destruction? # => true post.comments.length # => 2 id = post.comments.last.id Comment.find_by_id(id).nil? # => false post.save post.reload.comments.length # => 1 Comment.find_by_id(id).nil? # => true ROR Lab.

34. - common options - :class_name class Order < ActiveRecord::Base belongs_to :customer, :class_name => "Patron" end ROR Lab.

35. - common options - :conditions class Order < ActiveRecord::Base belongs_to :customer, :conditions => "active = 1" end ROR Lab.

36. - common options - :foreign_key class Order < ActiveRecord::Base belongs_to :customer, :class_name => "Patron", :foreign_key => "patron_id" end ROR Lab.

37. - common options - :include class LineItem < ActiveRecord::Base belongs_to :order, :include => :customer end class Order < ActiveRecord::Base belongs_to :customer has_many :line_items end class Customer < ActiveRecord::Base has_many :orders end ROR Lab.

38. - common options - :readonly class Customer < ActiveRecord::Base has_many :orders, :readonly => true end ROR Lab.

39. - common options - :select class Order < ActiveRecord::Base belongs_to :customer, :select => "name, proﬁle, group_id" end ROR Lab.

40. - common options - :validate class Order < ActiveRecord::Base belongs_to :customer, :validate => true end ROR Lab.

41. Common has_ Options has_one / has_many • :as • :order* (also, included in HABTM) • :primary_key • :source • :source_type • :through ROR Lab.

42. - common has_ options - :as class Picture < ActiveRecord::Base belongs_to :imageable, :polymorphic => true end class Employee < ActiveRecord::Base has_many :pictures, :as => :imageable end class Product < ActiveRecord::Base has_many :pictures, :as => :imageable end ROR Lab.

43. - common has_ options - :order class Post < ActiveRecord::Base has_many :comments, :order => ”updated_at” end •also, in HABTM ROR Lab.

44. - common has_ options - :primary_key class Order < ActiveRecord::Base default belongs_to :customer, :primary_key => "id", :foreign_key => "customer_id" class Order < ActiveRecord::Base belongs_to :customer, :class_name => "Patron", :primary_key => "civil_no", :foreign_key => "patron_id" ROR Lab.

45. - common has_ options - :source & :source_type class Tag < ActiveRecord::Base has_many :taggings, :dependent => :destroy has_many :books, :through => :tagings, :source => :taggable, :source_type => "Book" has_many :movies, :through => :tagings, :source => :taggable, :source_type => "Movie" end class Tagging < ActiveRecord::Base belongs_to :taggable, :polymorphic => true belongs_to :tag end class Book < ActiveRecord::Base has_many :taggings, :as => :taggable has_many :tags, :through => :taggings end class Movie < ActiveRecord::Base has_many :taggings, :as => :taggable has_many :tags, :through => :taggings end • http://www.brentmc79.com/posts/polymorphic-many-to-many-associations-in-rails ROR Lab.

46. - common has_ options - :through class Supplier < ActiveRecord::Base has_one :account has_one :account_history, :through => :account end class Account < ActiveRecord::Base belongs_to :supplier has_one :account_history end class AccountHistory < ActiveRecord::Base belongs_to :account end ROR Lab.

47. Common _many Options has_many / HABTM • :counter_sql • :extend • :ﬁnder_sql • :group • :limit • :offset • :uniq ROR Lab.

48. - common _many options - :finder_sql class Person < ActiveRecord::Base has_many :subscribers, :class_name => "Person", :finder_sql => Proc.new { %Q{ SELECT DISTINCT * FROM people p, post_subscriptions ps WHERE ps.post_id = #{id} AND ps.person_id = p.id ORDER BY p.first_name } } ROR Lab.

49. - common _many options - :counter_sql class Person < ActiveRecord::Base has_many :subscribers, :class_name => "Person", :counter_sql => Proc.new { %Q{ SELECT DISTINCT * FROM people p, post_subscriptions ps WHERE ps.post_id = #{id} AND ps.person_id = p.id ORDER BY p.ﬁrst_name } } ROR Lab.

50. - common _many options - :extend association proxy(or interface) class Customer < ActiveRecord::Base has_many :orders do def find_by_order_prefix(order_number) find_by_region_id(order_number[0..2]) end end ROR Lab.

51. - common _many options - :extend module FindRecentExtension def ﬁnd_recent where("created_at > ?", 5.days.ago) end end class Customer < ActiveRecord::Base has_many :orders, :extend => FindRecentExtension end class Supplier < ActiveRecord::Base has_many :deliveries, :extend => FindRecentExtension ROR Lab.

52. - common _many options - :extend class Customer < ActiveRecord::Base has_many :orders, :extend => [FindRecentExtension, FindActiveExtension] end ROR Lab.

53. - common _many options - * 3 AP accessors • proxy_association.owner • proxy_association.reﬂection • proxy_association.target AP* : Association Proxy ROR Lab.

54. - common _many options - :group class Customer < ActiveRecord::Base has_many :line_items, :through => :orders, :group => "orders.id" end ROR Lab.

55. - common _many options - :limit / :offset class Customer < ActiveRecord::Base has_many :recent_orders, :class_name => "Order", :order => "order_date DESC", :limit => 100 :offset => 300 ROR Lab.

56. - common _many options - :uniq class Person < ActiveRecord::Base has_many :readings has_many :posts, :through => :readings end person = Person.create(:name => 'john') post = Post.create(:name => 'a1') person.posts << post person.posts << post person.posts.inspect # => [#<Post id: 5, name: "a1">, #<Post id: 5, name: "a1">] Reading.all.inspect # => [#<Reading id: 12, person_id: 5, post_id: 5>, #<Reading id: 13, person_id: 5, post_id: 5>] ROR Lab.

57. - common _many options - :uniq class Person has_many :readings has_many :posts, :through => :readings, :uniq => true end person = Person.create(:name => 'honda') post = Post.create(:name => 'a1') person.posts << post person.posts << post person.posts.inspect # => [#<Post id: 7, name: "a1">] Reading.all.inspect # => [#<Reading id: 16, person_id: 7, post_id: 7>, #<Reading id: 17, person_id: 7, post_id: 7>] ROR Lab.

58. Common one-way Options belongs_to / has_one / has_many • :dependent class Comment < ActiveRecord::Base belongs_to :post, :dependent => :destroy end class Post < ActiveRecord::Base has_many :comments, :dependent => :destroy end ROR Lab.

59. Special Options • belongs_to • :counter_cache • :polymorphic • :touch • HABTM • :association_foreign_key • :delete_sql • :insert_sql • :join_table ROR Lab.

60. - special options for HABTM - :association_foreign_key class User < ActiveRecord::Base has_and_belongs_to_many :friends, :class_name => "User", :foreign_key => "this_user_id", :association_foreign_key => "other_user_id" many-to-many self join ROR Lab.

61. - special options for HABTM - :delete_sql class Developer < ActiveRecord::Base has_and_belongs_to_many :active_projects, :join_table => 'developers_projects', :delete_sql => "DELETE FROM developers_projects WHERE active=1 AND developer_id = #{id} AND project_id = #{record.id}" end ROR Lab.

62. - special options for HABTM - :insert_sql class Developer < ActiveRecord::Base has_and_belongs_to_many :active_projects, :join_table => 'developers_projects', :insert_sql => "INSERT INTO developers_projects VALUES(#{id},#{record.id})" end ROR Lab.

63. - special options for HABTM - :join_table class Category < ActiveRecord::Base has_and_belongs_to_many :products, :join_table => “cats_prods” end class Product < ActiveRecord::Base has_and_belongs_to_many :categories, :join_table => “cats_prods” default join table => “categories_products” ROR Lab.

64. Association Callbacks • in the lifecycle of a collection • before_add • after_add • before_remove • after_remove ROR Lab.

65. Association Callbacks class Customer < ActiveRecord::Base has_many :orders, :before_add => :check_credit_limit def check_credit_limit(order) ... end end class Customer < ActiveRecord::Base has_many :orders, :before_add => [:check_credit_limit, :calculate_shipping_charges] def check_credit_limit(order) ... end def calculate_shipping_charges(order) ... end ROR Lab.

66. Summary • http://jonathanhui.com/ruby-rails-3-model- association ROR Lab.

67. 감사합니다.

68. ROR Lab.

ActiveRecord Associations (2), Season 1

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