diff options
| -rwxr-xr-x | activerecord/lib/active_record/associations.rb | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb index d1382df7a1..7c60ab8fd0 100755 --- a/activerecord/lib/active_record/associations.rb +++ b/activerecord/lib/active_record/associations.rb @@ -203,7 +203,7 @@ module ActiveRecord # has_many :people, :extend => FindOrCreateByNameExtension # end # - # == Association Join Models + # === Association Join Models # # Has Many associations can be configured with the :through option to use an explicit join model to retrieve the data. This # operates similarly to a <tt>has_and_belongs_to_many</tt> association. The advantage is that you're able to add validations, @@ -243,6 +243,24 @@ module ActiveRecord # @firm.clients.collect { |c| c.invoices }.flatten # select all invoices for all clients of the firm # @firm.invoices # selects all invoices by going through the Client join model. # + # === Polymorphic Associations + # + # Polymorphic associations on models are not restricted on what types of models they can be associated with. Rather, they + # specify an interface that a has_many association must adhere to. + # + # class Asset < ActiveRecord::Base + # belongs_to :attachable, :polymorphic => true + # end + # + # class Post < ActiveRecord::Base + # has_many :assets, :as => :attachable # The <tt>:as</tt> option specifies the polymorphic interface to use. + # end + # + # @asset.attachable = @post + # + # This works by using a type column in addition to a foreign key to specify the associated record. In the Asset example, you'd need + # an attachable_id integer column and an attachable_type string column. + # # == Caching # # All of the methods are built on a simple caching principle that will keep the result of the last query around unless specifically @@ -465,6 +483,7 @@ module ActiveRecord # * <tt>:offset</tt>: An integer determining the offset from where the rows should be fetched. So at 5, it would skip the first 4 rows. # * <tt>:select</tt>: By default, this is * as in SELECT * FROM, but can be changed if you for example want to do a join, but not # include the joined columns. + # * <tt>:as</tt>: Specifies a polymorphic interface (See #belongs_to). # * <tt>:through</tt>: Specifies a Join Model to perform the query through. 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> # or <tt>has_many</tt> association. @@ -478,6 +497,7 @@ module ActiveRecord # has_many :people, :class_name => "Person", :conditions => "deleted = 0", :order => "name" # has_many :tracks, :order => "position", :dependent => :destroy # has_many :comments, :dependent => :nullify + # has_many :tags, :as => :taggable # has_many :subscribers, :through => :subscriptions, :source => :user # has_many :subscribers, :class_name => "Person", :finder_sql => # 'SELECT DISTINCT people.* ' + @@ -603,12 +623,14 @@ module ActiveRecord # is used on the associate class (such as a Post class). You can also specify a custom counter cache column by given that # name instead of a true/false value to this option (e.g., <tt>:counter_cache => :my_custom_counter</tt>.) # * <tt>:include</tt> - specify second-order associations that should be eager loaded when this object is loaded. + # # <tt>:polymorphic</tt> - specify this association is a polymorphic association by passing true. # # Option examples: # belongs_to :firm, :foreign_key => "client_of" # belongs_to :author, :class_name => "Person", :foreign_key => "author_id" # belongs_to :valid_coupon, :class_name => "Coupon", :foreign_key => "coupon_id", # :conditions => 'discounts > #{payments_count}' + # belongs_to :attachable, :polymorphic => true def belongs_to(association_id, options = {}) reflection = create_belongs_to_reflection(association_id, options) |