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Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 87 |
1 files changed, 75 insertions, 12 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index 38e46e4bf8..62e9270539 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -384,7 +384,7 @@ end The corresponding migration might look like this: ```ruby -class CreateSuppliers < ActiveRecord::Migration[5.0] +class CreateSuppliers < ActiveRecord::Migration[5.2] def change create_table :suppliers do |t| t.string :name @@ -392,7 +392,7 @@ class CreateSuppliers < ActiveRecord::Migration[5.0] end create_table :accounts do |t| - t.integer :supplier_id + t.bigint :supplier_id t.string :account_number t.timestamps end @@ -402,7 +402,7 @@ class CreateSuppliers < ActiveRecord::Migration[5.0] end ``` -NOTE: Using `t.integer :supplier_id` makes the foreign key naming obvious and explicit. In current versions of Rails, you can abstract away this implementation detail by using `t.references :supplier` instead. +NOTE: Using `t.bigint :supplier_id` makes the foreign key naming obvious and explicit. In current versions of Rails, you can abstract away this implementation detail by using `t.references :supplier` instead. ### Choosing Between `has_many :through` and `has_and_belongs_to_many` @@ -466,11 +466,11 @@ Similarly, you can retrieve `@product.pictures`. If you have an instance of the `Picture` model, you can get to its parent via `@picture.imageable`. To make this work, you need to declare both a foreign key column and a type column in the model that declares the polymorphic interface: ```ruby -class CreatePictures < ActiveRecord::Migration[5.0] +class CreatePictures < ActiveRecord::Migration[5.2] def change create_table :pictures do |t| t.string :name - t.integer :imageable_id + t.bigint :imageable_id t.string :imageable_type t.timestamps end @@ -619,11 +619,11 @@ end These need to be backed up by a migration to create the `assemblies_parts` table. This table should be created without a primary key: ```ruby -class CreateAssembliesPartsJoinTable < ActiveRecord::Migration[5.0] +class CreateAssembliesPartsJoinTable < ActiveRecord::Migration[5.2] def change create_table :assemblies_parts, id: false do |t| - t.integer :assembly_id - t.integer :part_id + t.bigint :assembly_id + t.bigint :part_id end add_index :assemblies_parts, :assembly_id @@ -1231,6 +1231,7 @@ The `has_one` association supports these options: * `:source` * `:source_type` * `:through` +* `:touch` * `:validate` ##### `:as` @@ -1305,10 +1306,47 @@ The `:source` option specifies the source association name for a `has_one :throu The `:source_type` option specifies the source association type for a `has_one :through` association that proceeds through a polymorphic association. +```ruby +class Book < ApplicationRecord + has_one :format, polymorphic: true + has_one :dust_jacket, through: :format, source: :dust_jacket, source_type: "Hardback" +end + +class Paperback < ApplicationRecord; end + +class Hardback < ApplicationRecord + has_one :dust_jacket +end + +class DustJacket < ApplicationRecord; end +``` + ##### `:through` The `:through` option specifies a join model through which to perform the query. `has_one :through` associations were discussed in detail [earlier in this guide](#the-has-one-through-association). +##### `:touch` + +If you set the `:touch` option to `true`, then the `updated_at` or `updated_on` timestamp on the associated object will be set to the current time whenever this object is saved or destroyed: + +```ruby +class Supplier < ApplicationRecord + has_one :account, touch: true +end + +class Account < ApplicationRecord + belongs_to :supplier +end +``` + +In this case, saving or destroying a supplier will update the timestamp on the associated account. You can also specify a particular timestamp attribute to update: + +```ruby +class Supplier < ApplicationRecord + has_one :account, touch: :suppliers_updated_at +end +``` + ##### `:validate` If you set the `:validate` option to `true`, then associated objects will be validated whenever you save this object. By default, this is `false`: associated objects will not be validated when this object is saved. @@ -1544,7 +1582,7 @@ The `collection.size` method returns the number of objects in the collection. ##### `collection.find(...)` The `collection.find` method finds objects within the collection. It uses the same syntax and options as -[`ActiveRecord::Base.find`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find). +[`ActiveRecord::Base.find`](https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find). ```ruby @available_book = @author.books.find(1) @@ -1563,7 +1601,7 @@ The `collection.where` method finds objects within the collection based on the c The `collection.exists?` method checks whether an object meeting the supplied conditions exists in the collection. It uses the same syntax and options as -[`ActiveRecord::Base.exists?`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-exists-3F). +[`ActiveRecord::Base.exists?`](https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-exists-3F). ##### `collection.build(attributes = {}, ...)` @@ -1717,6 +1755,20 @@ The `:source` option specifies the source association name for a `has_many :thro The `:source_type` option specifies the source association type for a `has_many :through` association that proceeds through a polymorphic association. +```ruby +class Author < ApplicationRecord + has_many :books + has_many :paperbacks, through: :books, source: :format, source_type: "Paperback" +end + +class Book < ApplicationRecord + has_one :format, polymorphic: true +end + +class Hardback < ApplicationRecord; end +class Paperback < ApplicationRecord; end +``` + ##### `:through` The `:through` option specifies a join model through which to perform the query. `has_many :through` associations provide a way to implement many-to-many relationships, as discussed [earlier in this guide](#the-has-many-through-association). @@ -2077,7 +2129,7 @@ The `collection.size` method returns the number of objects in the collection. ##### `collection.find(...)` The `collection.find` method finds objects within the collection. It uses the same syntax and options as -[`ActiveRecord::Base.find`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find). +[`ActiveRecord::Base.find`](https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find). ```ruby @assembly = @part.assemblies.find(1) @@ -2095,7 +2147,7 @@ The `collection.where` method finds objects within the collection based on the c The `collection.exists?` method checks whether an object meeting the supplied conditions exists in the collection. It uses the same syntax and options as -[`ActiveRecord::Base.exists?`](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-exists-3F). +[`ActiveRecord::Base.exists?`](https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-exists-3F). ##### `collection.build(attributes = {})` @@ -2350,6 +2402,17 @@ end If a `before_add` callback throws an exception, the object does not get added to the collection. Similarly, if a `before_remove` callback throws an exception, the object does not get removed from the collection. +NOTE: These callbacks are called only when the associated objects are added or removed through the association collection: + +```ruby +# Triggers `before_add` callback +author.books << book +author.books = [book, book2] + +# Does not trigger the `before_add` callback +book.update(author_id: 1) +``` + ### Association Extensions You're not limited to the functionality that Rails automatically builds into association proxy objects. You can also extend these objects through anonymous modules, adding new finders, creators, or other methods. For example: |