新手：越来越相互喜欢且仅当它们是相互有活动记录？ [英] newbie : getting mutual likes and only if they are mutual with active record?

问题描述

这将是一个很好的方式来获得相互的喜欢？其中，2用户喜欢对方（如在好友列表），并只得到谁拥有相互匹配的那些用户？

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 )

我已经尝试了一些加入的，但不能真正得到它的工作，有没有建筑物AR功能获得上述结果？

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?

推荐答案

要添加到jexact的回答，这是你可以做到这一点使用AR一种方式：

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')

或

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

这是另一种（？慢，但恕我直言，看起来比较清爽）的方法是做到这一点在您的用户模式（没有测试过，但应该给你一个想法）：

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

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