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Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 124 |
1 files changed, 70 insertions, 54 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index 22f6f5e7d6..95c7e747ef 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -1,3 +1,5 @@ +**DO NOT READ THIS FILE IN GITHUB, GUIDES ARE PUBLISHED IN http://guides.rubyonrails.org.** + Active Record Associations ========================== @@ -101,13 +103,13 @@ class CreateOrders < ActiveRecord::Migration def change create_table :customers do |t| t.string :name - t.timestamps + t.timestamps null: false end create_table :orders do |t| - t.belongs_to :customer + t.belongs_to :customer, index: true t.datetime :order_date - t.timestamps + t.timestamps null: false end end end @@ -132,13 +134,13 @@ class CreateSuppliers < ActiveRecord::Migration def change create_table :suppliers do |t| t.string :name - t.timestamps + t.timestamps null: false end create_table :accounts do |t| - t.belongs_to :supplier + t.belongs_to :supplier, index: true t.string :account_number - t.timestamps + t.timestamps null: false end end end @@ -165,13 +167,13 @@ class CreateCustomers < ActiveRecord::Migration def change create_table :customers do |t| t.string :name - t.timestamps + t.timestamps null: false end create_table :orders do |t| - t.belongs_to :customer + t.belongs_to :customer, index:true t.datetime :order_date - t.timestamps + t.timestamps null: false end end end @@ -207,19 +209,19 @@ class CreateAppointments < ActiveRecord::Migration def change create_table :physicians do |t| t.string :name - t.timestamps + t.timestamps null: false end create_table :patients do |t| t.string :name - t.timestamps + t.timestamps null: false end create_table :appointments do |t| - t.belongs_to :physician - t.belongs_to :patient + t.belongs_to :physician, index: true + t.belongs_to :patient, index: true t.datetime :appointment_date - t.timestamps + t.timestamps null: false end end end @@ -291,19 +293,19 @@ class CreateAccountHistories < ActiveRecord::Migration def change create_table :suppliers do |t| t.string :name - t.timestamps + t.timestamps null: false end create_table :accounts do |t| - t.belongs_to :supplier + t.belongs_to :supplier, index: true t.string :account_number - t.timestamps + t.timestamps null: false end create_table :account_histories do |t| - t.belongs_to :account + t.belongs_to :account, index: true t.integer :credit_rating - t.timestamps + t.timestamps null: false end end end @@ -332,17 +334,17 @@ class CreateAssembliesAndParts < ActiveRecord::Migration def change create_table :assemblies do |t| t.string :name - t.timestamps + t.timestamps null: false end create_table :parts do |t| t.string :part_number - t.timestamps + t.timestamps null: false end create_table :assemblies_parts, id: false do |t| - t.belongs_to :assembly - t.belongs_to :part + t.belongs_to :assembly, index: true + t.belongs_to :part, index: true end end end @@ -371,14 +373,16 @@ class CreateSuppliers < ActiveRecord::Migration def change create_table :suppliers do |t| t.string :name - t.timestamps + t.timestamps null: false end create_table :accounts do |t| t.integer :supplier_id t.string :account_number - t.timestamps + t.timestamps null: false end + + add_index :accounts, :supplier_id end end ``` @@ -453,8 +457,10 @@ class CreatePictures < ActiveRecord::Migration t.string :name t.integer :imageable_id t.string :imageable_type - t.timestamps + t.timestamps null: false end + + add_index :pictures, :imageable_id end end ``` @@ -466,8 +472,8 @@ class CreatePictures < ActiveRecord::Migration def change create_table :pictures do |t| t.string :name - t.references :imageable, polymorphic: true - t.timestamps + t.references :imageable, polymorphic: true, index: true + t.timestamps null: false end end end @@ -496,8 +502,8 @@ In your migrations/schema, you will add a references column to the model itself. class CreateEmployees < ActiveRecord::Migration def change create_table :employees do |t| - t.references :manager - t.timestamps + t.references :manager, index: true + t.timestamps null: false end end end @@ -561,6 +567,8 @@ class CreateOrders < ActiveRecord::Migration t.string :order_number t.integer :customer_id end + + add_index :orders, :customer_id end end ``` @@ -594,6 +602,9 @@ class CreateAssembliesPartsJoinTable < ActiveRecord::Migration t.integer :assembly_id t.integer :part_id end + + add_index :assemblies_parts, :assembly_id + add_index :assemblies_parts, :part_id end end ``` @@ -747,7 +758,7 @@ class Order < ActiveRecord::Base end ``` -Each instance of the order model will have these methods: +Each instance of the `Order` model will have these methods: ```ruby customer @@ -870,10 +881,12 @@ class Order < ActiveRecord::Base belongs_to :customer, counter_cache: :count_of_orders end class Customer < ActiveRecord::Base - has_many :orders + has_many :orders, counter_cache: :count_of_orders end ``` +NOTE: You only need to specify the :counter_cache option on the "has_many side" of the association when using a custom name for the counter cache. + Counter cache columns are added to the containing model's list of read-only attributes through `attr_readonly`. ##### `:dependent` @@ -1131,7 +1144,7 @@ The `has_one` association supports these options: ##### `:as` -Setting the `:as` option indicates that this is a polymorphic association. Polymorphic associations were discussed in detail <a href="#polymorphic-associations">earlier in this guide</a>. +Setting the `:as` option indicates that this is a polymorphic association. Polymorphic associations were discussed in detail [earlier in this guide](#polymorphic-associations). ##### `:autosave` @@ -1203,7 +1216,7 @@ The `:source_type` option specifies the source association type for a `has_one : ##### `:through` -The `:through` option specifies a join model through which to perform the query. `has_one :through` associations were discussed in detail <a href="#the-has-one-through-association">earlier in this guide</a>. +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). ##### `:validate` @@ -1312,9 +1325,9 @@ When you declare a `has_many` association, the declaring class automatically gai * `collection<<(object, ...)` * `collection.delete(object, ...)` * `collection.destroy(object, ...)` -* `collection=objects` +* `collection=(objects)` * `collection_singular_ids` -* `collection_singular_ids=ids` +* `collection_singular_ids=(ids)` * `collection.clear` * `collection.empty?` * `collection.size` @@ -1333,16 +1346,16 @@ class Customer < ActiveRecord::Base end ``` -Each instance of the customer model will have these methods: +Each instance of the `Customer` model will have these methods: ```ruby orders(force_reload = false) orders<<(object, ...) orders.delete(object, ...) orders.destroy(object, ...) -orders=objects +orders=(objects) order_ids -order_ids=ids +order_ids=(ids) orders.clear orders.empty? orders.size @@ -1390,7 +1403,7 @@ The `collection.destroy` method removes one or more objects from the collection WARNING: Objects will _always_ be removed from the database, ignoring the `:dependent` option. -##### `collection=objects` +##### `collection=(objects)` The `collection=` method makes the collection contain only the supplied objects, by adding and deleting as appropriate. @@ -1402,7 +1415,7 @@ The `collection_singular_ids` method returns an array of the ids of the objects @order_ids = @customer.order_ids ``` -##### `collection_singular_ids=ids` +##### `collection_singular_ids=(ids)` The `collection_singular_ids=` method makes the collection contain only the objects identified by the supplied primary key values, by adding and deleting as appropriate. @@ -1486,6 +1499,7 @@ The `has_many` association supports these options: * `:as` * `:autosave` * `:class_name` +* `:counter_cache` * `:dependent` * `:foreign_key` * `:inverse_of` @@ -1497,7 +1511,7 @@ The `has_many` association supports these options: ##### `:as` -Setting the `:as` option indicates that this is a polymorphic association, as discussed <a href="#polymorphic-associations">earlier in this guide</a>. +Setting the `:as` option indicates that this is a polymorphic association, as discussed [earlier in this guide](#polymorphic-associations). ##### `:autosave` @@ -1513,6 +1527,10 @@ class Customer < ActiveRecord::Base end ``` +##### `:counter_cache` + +This option can be used to configure a custom named `:counter_cache`. You only need this option when you customized the name of your `:counter_cache` on the [belongs_to association](#options-for-belongs-to). + ##### `:dependent` Controls what happens to the associated objects when their owner is destroyed: @@ -1523,8 +1541,6 @@ Controls what happens to the associated objects when their owner is destroyed: * `:restrict_with_exception` causes an exception to be raised if there are any associated records * `:restrict_with_error` causes an error to be added to the owner if there are any associated objects -NOTE: This option is ignored when you use the `:through` option on the association. - ##### `:foreign_key` By convention, Rails assumes that the column used to hold the foreign key on the other model is the name of this model with the suffix `_id` added. The `:foreign_key` option lets you set the name of the foreign key directly: @@ -1579,7 +1595,7 @@ The `:source_type` option specifies the source association type for a `has_many ##### `: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 <a href="#the-has-many-through-association">earlier in this guide</a>. +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). ##### `:validate` @@ -1632,7 +1648,7 @@ If you use a hash-style `where` option, then record creation via this associatio ##### `extending` -The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail <a href="#association-extensions">later in this guide</a>. +The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail [later in this guide](#association-extensions). ##### `group` @@ -1801,9 +1817,9 @@ When you declare a `has_and_belongs_to_many` association, the declaring class au * `collection<<(object, ...)` * `collection.delete(object, ...)` * `collection.destroy(object, ...)` -* `collection=objects` +* `collection=(objects)` * `collection_singular_ids` -* `collection_singular_ids=ids` +* `collection_singular_ids=(ids)` * `collection.clear` * `collection.empty?` * `collection.size` @@ -1822,16 +1838,16 @@ class Part < ActiveRecord::Base end ``` -Each instance of the part model will have these methods: +Each instance of the `Part` model will have these methods: ```ruby assemblies(force_reload = false) assemblies<<(object, ...) assemblies.delete(object, ...) assemblies.destroy(object, ...) -assemblies=objects +assemblies=(objects) assembly_ids -assembly_ids=ids +assembly_ids=(ids) assemblies.clear assemblies.empty? assemblies.size @@ -1886,7 +1902,7 @@ The `collection.destroy` method removes one or more objects from the collection @part.assemblies.destroy(@assembly1) ``` -##### `collection=objects` +##### `collection=(objects)` The `collection=` method makes the collection contain only the supplied objects, by adding and deleting as appropriate. @@ -1898,7 +1914,7 @@ The `collection_singular_ids` method returns an array of the ids of the objects @assembly_ids = @part.assembly_ids ``` -##### `collection_singular_ids=ids` +##### `collection_singular_ids=(ids)` The `collection_singular_ids=` method makes the collection contain only the objects identified by the supplied primary key values, by adding and deleting as appropriate. @@ -2082,7 +2098,7 @@ If you use a hash-style `where`, then record creation via this association will ##### `extending` -The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail <a href="#association-extensions">later in this guide</a>. +The `extending` method specifies a named module to extend the association proxy. Association extensions are discussed in detail [later in this guide](#association-extensions). ##### `group` |