newbie : getting mutual likes and only if they are mutual with active record?

Question

What would be a good way to get mutual likes ? where 2 users like each other ( as in a friendlist) and get only those users who have a mutual match?

user_id   | likes_id 
1           2                
2           1

Only get results where both of the users likes each other ( friendship )

I have tried some join's but can't really get it to work, is there a building AR feature to get the above results?

Answer 1

To add to jexact's answer this is one way you can do this using AR:

Like.joins('join likes l on likes.user_id=l.likes_id and l.user_id=likes.likes_id')

or

Like.select('l.*').joins('join likes l on likes.user_id=l.likes_id and l.user_id=likes.likes_id')

An alternative (slower? but imho looks cleaner) way is to do this in your User model (NOT tested, but should give you an idea):

class User < ActiveRecord::Base
  has_many :likes
  has_many :friends, :through => :likes

  has_many :liked_by, :foreign_key => 'likes_id', :class_name => 'Like'
  has_many :followers, :through => :liked_by, :source => :user

  def mutually_likes?(user)
    self.friends.include?(user) && self.followers.include?(user)
  end
end