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?
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
I think this is what you're looking for: ruby on rails getting a 2-way friend relationship in active record?
Alternatively you can try this:
SELECT a.user_id
FROM likes AS a
INNER JOIN likes AS b
ON a.user_id=b.likes_id
AND a.likes_id=b.user_id
http://railscasts.com/episodes/163-self-referential-association
this way you can create relations between users, like I used this exemple to create relations between Media Companies and Companies hwo owns this Media (in my case), where a Media could be owned by a company A, and company A is owned by Company B and this is where you get the Self-Referential Association.
In your case is much simpler to implement this as you need users models.. for me it took more modifications to do.
I made it with
@groups = Like.select('l.*').joins('join likes l on likes.user_id=l.likes and l.user_id=likes.likes')
unless @groups.empty?
@groups.each do |group|
friendship = Friendship.create(user_id: group.user_id, friend_id: group.likes)
end
end
The abstraction in model is nicer I look into that later on
