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Diffstat (limited to 'guides/source/association_basics.md')
| -rw-r--r-- | guides/source/association_basics.md | 25 |
1 files changed, 19 insertions, 6 deletions
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md index f75517c5ab..e076f10ece 100644 --- a/guides/source/association_basics.md +++ b/guides/source/association_basics.md @@ -1257,7 +1257,7 @@ Controls what happens to the associated object when its owner is destroyed: * `:destroy` causes the associated object to also be destroyed * `:delete` causes the associated object to be deleted directly from the database (so callbacks will not execute) -* `:nullify` causes the foreign key to be set to `NULL`. Callbacks are not executed. +* `:nullify` causes the foreign key to be set to `NULL`. Polymorphic type column is also nullified on polymorphic associations. Callbacks are not executed. * `:restrict_with_exception` causes an `ActiveRecord::DeleteRestrictionError` 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 @@ -1544,7 +1544,7 @@ 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 +1563,7 @@ 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 = {}, ...)` @@ -1658,10 +1658,12 @@ Controls what happens to the associated objects when their owner is destroyed: * `:destroy` causes all the associated objects to also be destroyed * `:delete_all` causes all the associated objects to be deleted directly from the database (so callbacks will not execute) -* `:nullify` causes the foreign keys to be set to `NULL`. Callbacks are not executed. +* `:nullify` causes the foreign key to be set to `NULL`. Polymorphic type column is also nullified on polymorphic associations. Callbacks are not executed. * `:restrict_with_exception` causes an `ActiveRecord::DeleteRestrictionError` 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 +The `:destroy` and `:delete_all` options also affect the semantics of the `collection.delete` and `collection=` methods by causing them to destroy associated objects when they are removed from the collection. + ##### `: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: @@ -2075,7 +2077,7 @@ 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) @@ -2093,7 +2095,7 @@ 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 = {})` @@ -2348,6 +2350,17 @@ 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: |