I made table in database as follows:
create_table "friendships", :force => true do |t|
t.column "owner_id", :integer, :null => false
t.column "friend_id", :integer, :null => false
In the model, put:
class Friendship < ActiveRecord::Base
belongs_to :owner, :class_name => "User", :foreign_key => :owner_id
belongs_to :friend, :class_name => "User", :foreign_key => :friend_id
Then in the table that you want to act as friendable, you put:
class User < ActiveRecord::Base
And that's it. you can now access friends() and friendships() of a person.
However, it doesn't work when you try to push the association through, like:
user = User.find(1)
friend = User.find(2)
user.friends << friend
It will fail complain about how "user_id" doesn't exist in any of the tables. I was scratching my head for a good 2 hours before I figured that it wasn't actually me this time. I think the << method doesn't correctly use the foreign keys correctly when they're non-standard like this. According to #6466 ([PATCH] fix for has_many :through push and delete with legacy/non-standard foreign_keys), this doesn't work, until a patch is written for it. I'm not as familiar with the Rails code base as I should be. This is probably a good chance to get started looking at it...unless someone else fixes it first...
As a workaround, I simply used the Friendship ActiveRecord object directly to create the association. I'll have to override the method in the plugin so that it allows correct use of << for my specific case. Tip!