diff options
Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 77 |
1 files changed, 50 insertions, 27 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index 5794bfa666..9616647f15 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -599,7 +599,7 @@ class CreateBooks < ActiveRecord::Migration[5.0] t.string :book_number t.integer :author_id end - + add_index :books, :author_id add_foreign_key :books, :authors end @@ -663,11 +663,11 @@ By default, associations look for objects only within the current module's scope module MyApplication module Business class Supplier < ApplicationRecord - has_one :account + has_one :account end class Account < ApplicationRecord - belongs_to :supplier + belongs_to :supplier end end end @@ -679,13 +679,13 @@ This will work fine, because both the `Supplier` and the `Account` class are def module MyApplication module Business class Supplier < ApplicationRecord - has_one :account + has_one :account end end module Billing class Account < ApplicationRecord - belongs_to :supplier + belongs_to :supplier end end end @@ -697,14 +697,14 @@ To associate a model with a model in a different namespace, you must specify the module MyApplication module Business class Supplier < ApplicationRecord - has_one :account, + has_one :account, class_name: "MyApplication::Billing::Account" end end module Billing class Account < ApplicationRecord - belongs_to :supplier, + belongs_to :supplier, class_name: "MyApplication::Business::Supplier" end end @@ -811,6 +811,7 @@ When you declare a `belongs_to` association, the declaring class automatically g * `build_association(attributes = {})` * `create_association(attributes = {})` * `create_association!(attributes = {})` +* `reload_association` In all of these methods, `association` is replaced with the symbol passed as the first argument to `belongs_to`. For example, given the declaration: @@ -828,6 +829,7 @@ author= build_author create_author create_author! +reload_author ``` NOTE: When initializing a new `has_one` or `belongs_to` association you must use the `build_` prefix to build the association, rather than the `association.build` method that would be used for `has_many` or `has_and_belongs_to_many` associations. To create one, use the `create_` prefix. @@ -840,10 +842,10 @@ The `association` method returns the associated object, if any. If no associated @author = @book.author ``` -If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload` on the parent object. +If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload_association` on the parent object. ```ruby -@author = @book.reload.author +@author = @book.reload_author ``` ##### `association=(associate)` @@ -904,7 +906,7 @@ The `belongs_to` association supports these options: ##### `:autosave` -If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object. +If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved. ##### `:class_name` @@ -960,19 +962,18 @@ class Author < ApplicationRecord end ``` -NOTE: You only need to specify the :counter_cache option on the `belongs_to` +NOTE: You only need to specify the `:counter_cache` option on the `belongs_to` side of the association. Counter cache columns are added to the containing model's list of read-only attributes through `attr_readonly`. ##### `:dependent` -Controls what happens to associated objects when their owner is destroyed: +If you set the `:dependent` option to: -* `:destroy` causes the associated objects to also be destroyed. -* `:delete_all` causes the associated objects to be deleted directly from the database (callbacks are not executed). -* `:nullify` causes the foreign keys to be set to `NULL` (callbacks are not executed). -* `:restrict_with_exception` causes an exception to be raised if there are associated records. -* `:restrict_with_error` causes an error to be added to the owner if there are associated objects. +* `:destroy`, when the object is destroyed, `destroy` will be called on its +associated objects. +* `:delete`, when the object is destroyed, all its associated objects will be +deleted directly from the database without calling their `destroy` method. WARNING: You should not specify this option on a `belongs_to` association that is connected with a `has_many` association on the other class. Doing so can lead to orphaned records in your database. @@ -1161,6 +1162,7 @@ When you declare a `has_one` association, the declaring class automatically gain * `build_association(attributes = {})` * `create_association(attributes = {})` * `create_association!(attributes = {})` +* `reload_association` In all of these methods, `association` is replaced with the symbol passed as the first argument to `has_one`. For example, given the declaration: @@ -1178,6 +1180,7 @@ account= build_account create_account create_account! +reload_account ``` NOTE: When initializing a new `has_one` or `belongs_to` association you must use the `build_` prefix to build the association, rather than the `association.build` method that would be used for `has_many` or `has_and_belongs_to_many` associations. To create one, use the `create_` prefix. @@ -1190,10 +1193,10 @@ The `association` method returns the associated object, if any. If no associated @account = @supplier.account ``` -If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload` on the parent object. +If the associated object has already been retrieved from the database for this object, the cached version will be returned. To override this behavior (and force a database read), call `#reload_association` on the parent object. ```ruby -@account = @supplier.reload.account +@account = @supplier.reload_account ``` ##### `association=(associate)` @@ -1254,7 +1257,7 @@ Setting the `:as` option indicates that this is a polymorphic association. Polym ##### `:autosave` -If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object. +If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved. ##### `:class_name` @@ -1417,7 +1420,7 @@ If either of these saves fails due to validation errors, then the assignment sta If the parent object (the one declaring the `has_one` association) is unsaved (that is, `new_record?` returns `true`) then the child objects are not saved. They will automatically when the parent object is saved. -If you want to assign an object to a `has_one` association without saving the object, use the `association.build` method. +If you want to assign an object to a `has_one` association without saving the object, use the `build_association` method. ### `has_many` Association Reference @@ -1443,6 +1446,7 @@ When you declare a `has_many` association, the declaring class automatically gai * `collection.build(attributes = {}, ...)` * `collection.create(attributes = {})` * `collection.create!(attributes = {})` +* `collection.reload` In all of these methods, `collection` is replaced with the symbol passed as the first argument to `has_many`, and `collection_singular` is replaced with the singularized version of that symbol. For example, given the declaration: @@ -1471,11 +1475,12 @@ books.exists?(...) books.build(attributes = {}, ...) books.create(attributes = {}) books.create!(attributes = {}) +books.reload ``` ##### `collection` -The `collection` method returns an array of all of the associated objects. If there are no associated objects, it returns an empty array. +The `collection` method returns a Relation of all of the associated objects. If there are no associated objects, it returns an empty Relation. ```ruby @books = @author.books @@ -1559,7 +1564,7 @@ The `collection.size` method returns the number of objects in the collection. The `collection.find` method finds objects within the collection. It uses the same syntax and options as `ActiveRecord::Base.find`. ```ruby -@available_books = @author.books.find(1) +@available_book = @author.books.find(1) ``` ##### `collection.where(...)` @@ -1609,6 +1614,14 @@ The `collection.create` method returns a single or array of new objects of the a Does the same as `collection.create` above, but raises `ActiveRecord::RecordInvalid` if the record is invalid. +##### `collection.reload` + +The `collection.reload` method returns a Relation of all of the associated objects, forcing a database read. If there are no associated objects, it returns an empty Relation. + +```ruby +@books = @author.books.reload +``` + #### Options for `has_many` While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_many` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: @@ -1640,7 +1653,7 @@ Setting the `:as` option indicates that this is a polymorphic association, as di ##### `:autosave` -If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object. +If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved. ##### `:class_name` @@ -1831,7 +1844,7 @@ The `limit` method lets you restrict the total number of objects that will be fe class Author < ApplicationRecord has_many :recent_books, -> { order('published_at desc').limit(100) }, - class_name: "Book", + class_name: "Book" end ``` @@ -1965,6 +1978,7 @@ When you declare a `has_and_belongs_to_many` association, the declaring class au * `collection.build(attributes = {})` * `collection.create(attributes = {})` * `collection.create!(attributes = {})` +* `collection.reload` In all of these methods, `collection` is replaced with the symbol passed as the first argument to `has_and_belongs_to_many`, and `collection_singular` is replaced with the singularized version of that symbol. For example, given the declaration: @@ -1993,6 +2007,7 @@ assemblies.exists?(...) assemblies.build(attributes = {}, ...) assemblies.create(attributes = {}) assemblies.create!(attributes = {}) +assemblies.reload ``` ##### Additional Column Methods @@ -2004,7 +2019,7 @@ WARNING: The use of extra attributes on the join table in a `has_and_belongs_to_ ##### `collection` -The `collection` method returns an array of all of the associated objects. If there are no associated objects, it returns an empty array. +The `collection` method returns a Relation of all of the associated objects. If there are no associated objects, it returns an empty Relation. ```ruby @assemblies = @part.assemblies @@ -2116,6 +2131,14 @@ The `collection.create` method returns a new object of the associated type. This Does the same as `collection.create`, but raises `ActiveRecord::RecordInvalid` if the record is invalid. +##### `collection.reload` + +The `collection.reload` method returns a Relation of all of the associated objects, forcing a database read. If there are no associated objects, it returns an empty Relation. + +```ruby +@assemblies = @part.assemblies.reload +``` + #### Options for `has_and_belongs_to_many` While Rails uses intelligent defaults that will work well in most situations, there may be times when you want to customize the behavior of the `has_and_belongs_to_many` association reference. Such customizations can easily be accomplished by passing options when you create the association. For example, this association uses two such options: @@ -2153,7 +2176,7 @@ end ##### `:autosave` -If you set the `:autosave` option to `true`, Rails will save any loaded members and destroy members that are marked for destruction whenever you save the parent object. +If you set the `:autosave` option to `true`, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Setting `:autosave` to `false` is not the same as not setting the `:autosave` option. If the `:autosave` option is not present, then new associated objects will be saved, but updated associated objects will not be saved. ##### `:class_name` |