Ruby on Rails的获得在活动记录一个2路的朋友关系？ [英] ruby on rails getting a 2-way friend relationship in active record?

问题描述

我试着去弄清楚如何做一个相互2路的关系，那就是：

Im trying to figure out how to do a mutual 2-way relationship, that is:

user_id  friend_id
  1          2
  2          1

在上面的用户1和用户2会成为朋友，如果两个 USER_ID = 1 的 friend_id = 2 和 friend_id = 2 的 USER_ID = 2 因为有朋友在表格中。如何计数的ActiveRecord所有的2路相互之间的关系？

In above user 1 and user 2 would be friends if both user_id = 1 has friend_id = 2 and friend_id = 2 has user_id = 2 as there friend in a table. How to count all the 2-way mutual relations in ActiveRecord?

推荐答案

您要查找的内容是的 has_​​and_belongs_to_many 关系：

What you're looking for is a has_and_belongs_to_many relationship:

class User < ActiveRecord::Base
  has_and_belongs_to_many :friends, :class_name => "User",
                                    :foreign_key => "this_user_id",
                                    :association_foreign_key => "other_user_id"
end

例是从<一个href="http://guides.rubyonrails.org/association_basics.html#has_and_belongs_to_many-association_foreign_key"相对=nofollow>§4.4.2.1。

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