diff options
| -rw-r--r-- | activerecord/lib/active_record/associations.rb | 15 | ||||
| -rw-r--r-- | railties/guides/source/association_basics.textile | 10 |
2 files changed, 21 insertions, 4 deletions
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb index 4caa434fc0..eebbd17f43 100644 --- a/activerecord/lib/active_record/associations.rb +++ b/activerecord/lib/active_record/associations.rb @@ -768,15 +768,20 @@ module ActiveRecord # Objects will be in addition destroyed if they're associated with <tt>:dependent => :destroy</tt>, # and deleted if they're associated with <tt>:dependent => :delete_all</tt>. # [collection=objects] - # Replaces the collections content by deleting and adding objects as appropriate. + # Replaces the collections content by deleting and adding objects as appropriate. If the <tt>:through</tt> + # option is true callbacks in the join models are triggered except destroy callbacks, since deletion is + # direct. # [collection_singular_ids] # Returns an array of the associated objects' ids # [collection_singular_ids=ids] - # Replace the collection with the objects identified by the primary keys in +ids+ + # Replace the collection with the objects identified by the primary keys in +ids+. This + # method loads the models and calls <tt>collection=</tt>. See above. # [collection.clear] # Removes every object from the collection. This destroys the associated objects if they # are associated with <tt>:dependent => :destroy</tt>, deletes them directly from the # database if <tt>:dependent => :delete_all</tt>, otherwise sets their foreign keys to +NULL+. + # If the <tt>:through</tt> option is true no destroy callbacks are invoked on the join models. + # Join models are directly deleted. # [collection.empty?] # Returns +true+ if there are no associated objects. # [collection.size] @@ -869,9 +874,11 @@ module ActiveRecord # [:as] # Specifies a polymorphic interface (See <tt>belongs_to</tt>). # [:through] - # Specifies a Join Model through which to perform the query. Options for <tt>:class_name</tt> and <tt>:foreign_key</tt> + # Specifies a join model through which to perform the query. Options for <tt>:class_name</tt> and <tt>:foreign_key</tt> # are ignored, as the association uses the source reflection. You can only use a <tt>:through</tt> query through a <tt>belongs_to</tt> - # <tt>has_one</tt> or <tt>has_many</tt> association on the join model. + # <tt>has_one</tt> or <tt>has_many</tt> association on the join model. The collection of join models can be managed via the collection + # API. For example, new join models are created for newly associated objects, and if some are gone their rows are deleted (directly, + # no destroy callbacks are triggered). # [:source] # Specifies the source association name used by <tt>has_many :through</tt> queries. Only use it if the name cannot be # inferred from the association. <tt>has_many :subscribers, :through => :subscriptions</tt> will look for either <tt>:subscribers</tt> or diff --git a/railties/guides/source/association_basics.textile b/railties/guides/source/association_basics.textile index 335d17579d..c69f2ae8c9 100644 --- a/railties/guides/source/association_basics.textile +++ b/railties/guides/source/association_basics.textile @@ -137,6 +137,16 @@ end !images/has_many_through.png(has_many :through Association Diagram)! +The collection of join models can be managed via the API. For example, if you assign + +<ruby> +physician.patients = patients +</ruby> + +new join models are created for newly associated objects, and if some are gone their rows are deleted. + +WARNING: Automatic deletion of join models is direct, no destroy callbacks are triggered. + The +has_many :through+ association is also useful for setting up "shortcuts" through nested +has_many+ associations. For example, if a document has many sections, and a section has many paragraphs, you may sometimes want to get a simple collection of all paragraphs in the document. You could set that up this way: <ruby> |