has_many conversely

rubyonrails-talk
1

I have a very simple association: class User < ActiveRecord::Base   has_and_belongs_to_many :friends,     :class_name=>"User",     :join_table=>"friends_users",     :association_foreign_key=>"friend_id",     :foreign_key=>"user_id"

User.friends - returns my friends. How can i get users who "friended" me? Thanks.

2

FriendUser.find(:all, :conditions => [‘friend_id = ?’,user.id]).collect{|x|x.user}

so I think you can put that in a model function

def befriended_ones FriendUser.find (:all, :conditions => [‘friend_id = ?’,user.id]).collect{|x|x.user} end

I would like to know if there is a way of doing this just using associations…

3

Right, Ivor. I knew about this way, and also would like to know if there is a way to do it through associations. And another issue, i have rich join model via has_many :through. And collection's clear (user.groups.clear) method works strange. It just clears collection in memory and doesn't touch join table at all. Even not nullify foreign keys, nothing. Is it expected?

4

Did you try reversing the habtm relationship manually:     has_and_belongs_to_many :friended,      :class_name => "User"      :join_table => "friends_users",     :association_foreign_key => "user_id",     :foreign_key => "friend_id"

You could build a plugin or function that did both ways, if you use self-relations like this often. Otherwise, I don't know anything built into Rails that does it both ways.

- Hal

5

Kane, I would appreciate it if you could give this a spin and let me know if it worked. thanks Ivor

6

It's really simple! How i didn't come to this from the beginning. From the 1st sight i think it should work. P.S fast test shows - it really works.