diff options
Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 60 |
1 files changed, 29 insertions, 31 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index 09ab64837a..4977d4f30e 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| @@ -388,13 +388,13 @@ 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.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 @@ -545,12 +545,12 @@ 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 +author.books.reload.empty? # discards the cached copy of books # and goes back to the database ``` @@ -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: - -* `: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 +Controls what happens to associated objects when their owner is destroyed: + +* `: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. |