Question

Given the following two models:

User (id)
FbFriendCache(user_id,fb_user_id)

I would like to be able to do : @user.facebook_friends

Which would return @users from the user model

I’ve tried:

class User < ActiveRecord::Base

  has_many :fb_friends,
    :through => :fb_friend_cache,
    :foreign_key => "fb_user_id"

But that fails w Could not find the association.

Ideas? Thanks

Answer 1

I am posting this as an answer as I am not able to provide the documentation snippet in comments. Ryan’s solution requires a tweak.

The foreign_key property is ignored for has_many :through associations. You should use source property instead.

:through

Specifies an association through which to perform the query.
This can be any other type of association, including other :through
associations. Options for :class_name, :primary_key and :foreign_key
are ignored, as the association uses the source reflection.

..

:source

Specifies the source association name used by has_many
:through queries. Only use it if the name cannot be inferred from the
association. has_many :subscribers, :through => :subscriptions will
look for either :subscribers or :subscriber on Subscription, unless a
:source is given.

Following solution should work:

class User < ActiveRecord::Base
  has_many :fb_friend_cache
  has_many :facebook_friends, :through => :fb_friend_cache, :source => :fb_user
end

class FbFriendCache < ActiveRecord::Base
  belongs_to :user
  belongs_to :fb_user, :class_name=>"User"
end