diff options
Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 80 |
1 files changed, 38 insertions, 42 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index 09ab64837a..03d3daecc8 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -105,13 +105,13 @@ class CreateBooks < ActiveRecord::Migration[5.0] def change create_table :authors do |t| t.string :name - t.timestamps null: false + t.timestamps end create_table :books do |t| t.belongs_to :author, index: true t.datetime :published_at - t.timestamps null: false + t.timestamps end end end @@ -136,13 +136,13 @@ class CreateSuppliers < ActiveRecord::Migration[5.0] def change create_table :suppliers do |t| t.string :name - t.timestamps null: false + t.timestamps end create_table :accounts do |t| t.belongs_to :supplier, index: true t.string :account_number - t.timestamps null: false + t.timestamps end end end @@ -180,13 +180,13 @@ class CreateAuthors < ActiveRecord::Migration[5.0] def change create_table :authors do |t| t.string :name - t.timestamps null: false + t.timestamps end create_table :books do |t| t.belongs_to :author, index: true t.datetime :published_at - t.timestamps null: false + t.timestamps end end end @@ -222,19 +222,19 @@ class CreateAppointments < ActiveRecord::Migration[5.0] def change create_table :physicians do |t| t.string :name - t.timestamps null: false + t.timestamps end create_table :patients do |t| t.string :name - t.timestamps null: false + t.timestamps end create_table :appointments do |t| t.belongs_to :physician, index: true t.belongs_to :patient, index: true t.datetime :appointment_date - t.timestamps null: false + t.timestamps end end end @@ -308,19 +308,19 @@ class CreateAccountHistories < ActiveRecord::Migration[5.0] def change create_table :suppliers do |t| t.string :name - t.timestamps null: false + t.timestamps end create_table :accounts do |t| t.belongs_to :supplier, index: true t.string :account_number - t.timestamps null: false + t.timestamps end create_table :account_histories do |t| t.belongs_to :account, index: true t.integer :credit_rating - t.timestamps null: false + t.timestamps end end end @@ -349,12 +349,12 @@ class CreateAssembliesAndParts < ActiveRecord::Migration[5.0] def change create_table :assemblies do |t| t.string :name - t.timestamps null: false + t.timestamps end create_table :parts do |t| t.string :part_number - t.timestamps null: false + t.timestamps end create_table :assemblies_parts, id: false do |t| @@ -387,14 +387,14 @@ The corresponding migration might look like this: class CreateSuppliers < ActiveRecord::Migration[5.0] def change create_table :suppliers do |t| - t.string :name - t.timestamps null: false + t.string :name + t.timestamps end create_table :accounts do |t| t.integer :supplier_id t.string :account_number - t.timestamps null: false + t.timestamps end add_index :accounts, :supplier_id @@ -472,7 +472,7 @@ class CreatePictures < ActiveRecord::Migration[5.0] t.string :name t.integer :imageable_id t.string :imageable_type - t.timestamps null: false + t.timestamps end add_index :pictures, [:imageable_type, :imageable_id] @@ -488,7 +488,7 @@ class CreatePictures < ActiveRecord::Migration[5.0] create_table :pictures do |t| t.string :name t.references :imageable, polymorphic: true, index: true - t.timestamps null: false + t.timestamps end end end @@ -518,7 +518,7 @@ class CreateEmployees < ActiveRecord::Migration[5.0] def change create_table :employees do |t| t.references :manager, index: true - t.timestamps null: false + t.timestamps end end end @@ -545,13 +545,13 @@ author.books.size # uses the cached copy of books author.books.empty? # uses the cached copy of books ``` -But what if you want to reload the cache, because data might have been changed by some other part of the application? Just pass `true` to the association call: +But what if you want to reload the cache, because data might have been changed by some other part of the application? Just call `reload` on the association: ```ruby author.books # retrieves books from the database author.books.size # uses the cached copy of books -author.books(true).empty? # discards the cached copy of books - # and goes back to the database +author.books.reload.empty? # discards the cached copy of books + # and goes back to the database ``` ### Avoiding Name Collisions @@ -734,7 +734,7 @@ end With these changes, Active Record will only load one copy of the author object, preventing inconsistencies and making your application more efficient: ```ruby -a = author.first +a = Author.first b = a.books.first a.first_name == b.author.first_name # => true a.first_name = 'Manny' @@ -932,15 +932,13 @@ side of the association. Counter cache columns are added to the containing model's list of read-only attributes through `attr_readonly`. ##### `:dependent` -If you set the `:dependent` option to: +Controls what happens to associated objects when their owner is destroyed: -* `:destroy`, when the object is destroyed, `destroy` will be called on its -associated objects. -* `:delete_all`, when the object is destroyed, all its associated objects will be -deleted directly from the database without calling their `destroy` method. -* `:nullify`, causes the foreign key to be set to `NULL`. Callbacks are not executed. -* `:restrict_with_exception`, causes an exception to be raised if there is an associated record -* `:restrict_with_error`, causes an error to be added to the owner if there is an associated object +* `: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. 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. @@ -1009,7 +1007,7 @@ class Author < ApplicationRecord end ``` -In this case, saving or destroying an book will update the timestamp on the associated author. You can also specify a particular timestamp attribute to update: +In this case, saving or destroying a book will update the timestamp on the associated author. You can also specify a particular timestamp attribute to update: ```ruby class Book < ApplicationRecord @@ -1479,7 +1477,7 @@ WARNING: Objects will _always_ be removed from the database, ignoring the `:depe ##### `collection=(objects)` -The `collection=` method makes the collection contain only the supplied objects, by adding and deleting as appropriate. +The `collection=` method makes the collection contain only the supplied objects, by adding and deleting as appropriate. The changes are persisted to the database. ##### `collection_singular_ids` @@ -1491,7 +1489,7 @@ The `collection_singular_ids` method returns an array of the ids of the objects ##### `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. +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. The changes are persisted to the database. ##### `collection.clear` @@ -1843,7 +1841,7 @@ article = Article.create(name: 'a1') person.articles << article person.articles << article person.articles.inspect # => [#<Article id: 5, name: "a1">, #<Article id: 5, name: "a1">] -Reading.all.inspect # => [#<Reading id: 12, person_id: 5, article_id: 5>, #<Reading id: 13, person_id: 5, article_id: 5>] +Reading.all.inspect # => [#<Reading id: 12, person_id: 5, article_id: 5>, #<Reading id: 13, person_id: 5, article_id: 5>] ``` In the above case there are two readings and `person.articles` brings out both of @@ -1862,7 +1860,7 @@ article = Article.create(name: 'a1') person.articles << article person.articles << article person.articles.inspect # => [#<Article id: 7, name: "a1">] -Reading.all.inspect # => [#<Reading id: 16, person_id: 7, article_id: 7>, #<Reading id: 17, person_id: 7, article_id: 7>] +Reading.all.inspect # => [#<Reading id: 16, person_id: 7, article_id: 7>, #<Reading id: 17, person_id: 7, article_id: 7>] ``` In the above case there are still two readings. However `person.articles` shows @@ -1996,11 +1994,9 @@ The `collection.delete` method removes one or more objects from the collection b @part.assemblies.delete(@assembly1) ``` -WARNING: This does not trigger callbacks on the join records. - ##### `collection.destroy(object, ...)` -The `collection.destroy` method removes one or more objects from the collection by running `destroy` on each record in the join table, including running callbacks. This does not destroy the objects. +The `collection.destroy` method removes one or more objects from the collection by deleting records in the join table. This does not destroy the objects. ```ruby @part.assemblies.destroy(@assembly1) @@ -2008,7 +2004,7 @@ The `collection.destroy` method removes one or more objects from the collection ##### `collection=(objects)` -The `collection=` method makes the collection contain only the supplied objects, by adding and deleting as appropriate. +The `collection=` method makes the collection contain only the supplied objects, by adding and deleting as appropriate. The changes are persisted to the database. ##### `collection_singular_ids` @@ -2020,7 +2016,7 @@ The `collection_singular_ids` method returns an array of the ids of the objects ##### `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. +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. The changes are persisted to the database. ##### `collection.clear` |