Flowdock

Class deprecated or moved

This class is deprecated or moved on the latest stable version. The last existing version (v3.0.9) is shown here.

Active Record Associations

This is the root class of all association proxies:

AssociationProxy
  BelongsToAssociation
    HasOneAssociation
  BelongsToPolymorphicAssociation
  AssociationCollection
    HasAndBelongsToManyAssociation
    HasManyAssociation
      HasManyThroughAssociation
         HasOneThroughAssociation

Association proxies in Active Record are middlemen between the object that holds the association, known as the @owner, and the actual associated object, known as the @target. The kind of association any proxy is about is available in @reflection. That’s an instance of the class ActiveRecord::Reflection::AssociationReflection.

For example, given

class Blog < ActiveRecord::Base
  has_many :posts
end

blog = Blog.find(:first)

the association proxy in blog.posts has the object in blog as @owner, the collection of its posts as @target, and the @reflection object represents a :has_many macro.

This class has most of the basic instance methods removed, and delegates unknown methods to @target via method_missing. As a corner case, it even removes the class method and that’s why you get

blog.posts.class # => Array

though the object behind blog.posts is not an Array, but an ActiveRecord::Associations::HasManyAssociation.

The @target object is not loaded until needed. For example,

blog.posts.count

is computed directly through SQL and does not trigger by itself the instantiation of the actual post records.

Show files where this class is defined (1 file)
Register or log in to add new notes.