控制器计数关系中的自引用查找 [英] Self-referential find in controller count relations

问题描述

为了在用户的显示页面上显示这些记录，我很难拔出一组与用户自相关的记录。

<用户（ current_user ）评价两个其他用户之间的兼容性（<$ c $> c> user_a 和 user_b ）。他们可以对兼容性进行正面或负面评价：对两个用户进行兼容评级，在user_a和user_b之间创建一个 positive_connection ，并将它们评为不兼容，创建一个 negative_connection 。因此，有positive_connection，negative_connection和用户的模型。$ ​​b
$现在我只需要显示 overall_positively_connected_to（@user）。

positive_connections_to

用户模式：

这是我需要的地方，但是我不能进一步：

  def overall_positive_connected_to（user）
 positive_connections_to（user）.count> negative_connections_to（user）.count 
 end 
 
 $ b def positive_connections_to（user）
 positive_connections.where（user_b_id =？，user）
 end 
 
 def negative_connections_to（user）
 negative_connections.where（user_b_id =？，user）
 end 
  

控制器

  @ user.user_bs.each do | user_b | 
 if user_b.overall_pos_connected_to（@user）
 @compatibles = user_b 
 end 
 end 
  

控制器中的代码显然是错误的，但是我应该怎么做呢？我完全不熟悉rails（和sql），所以可能做了一些天真的事。

任何帮助都会很棒。

• 用户（id ，名称）


• PositiveConnection（user_a_id，user_b_id）


• NegativeConnection（user_a_id，user_b_id）
  

或类似的东西。

我想你只需要2个模型
，为了方便，我打算将关系重命名为from_user和to_user
$ b

• 用户（id，name）


• 连接（value：integer，from_user_id，to_user_id）
  
  
  其中值为-1的负
  和+1正确。
  
  现在我们可以做一些类似于
  的事情（注意：你需要清楚确切的语法，例如：foreign_key，：source和stuff ）

    class User 
   $ b $ has_many：connections，：foreign_key => from_user_id
   has_many：connected_users，：through => ：connections，：source => ：to_user 
   $ b def positive_connections 
   connections.where（：value => 1）
   end 
   
   def negative_connections 
   ... 
   end 
   
   end 
    

  但是我们现在也有一个框架创建一个复杂的SQL查询
（同样你需要填写空格...但类似的东西）

$ $ p $ $ $ $ $ $ $用户

def positive_connected_users
connected_users.joins（：connections）.group（from_user_id）。having（SUM（connections.value）> 0）
end

end


  这并不完全符合
  的要求，是一种真正的解决方案的伪代码

  
  
  

  （这可能是更好地思考在纯SQL语言）

   SELECT用户。* FROM用户
   INNER JOIN连接ON to_user_id = users.id 
   WHERE from_user_id =＃{user.id} 
   HAVING SUM .value）> 0 
    

  
  

  I'm having real trouble pulling out a set of records that are self-referentially related to a user in order to show these on a user's 'show' page.

  Here's the idea:

  Users (current_user) rate the compatibility between two other users (user_a and user_b). They can rate compatibility either positively or negatively: rating two users "compatible" creates a positive_connection between user_a and user_b, and rating them "incompatible" creates a negative_connection. So there are models for positive_connection, negative_connection and user.

  Now I need to display only users that are overall_positively_connected_to(@user) (i.e. where positive_connections_to(@user).count > negative_connections_to(@user).count).

  This is where I've got to, but I can't get any further:

  User model:

    def overall_positive_connected_to(user)
        positive_connections_to(user).count > negative_connections_to(user).count
    end
  
  
    def positive_connections_to(user)
        positive_connections.where("user_b_id = ?", user)
    end     
  
    def negative_connections_to(user) 
        negative_connections.where("user_b_id = ?", user)
    end
  

  Controller

  @user.user_bs.each do |user_b|
    if user_b.overall_pos_connected_to(@user)
      @compatibles = user_b
    end
  end
  

  The code in the controller is clearly wrong, but how should I go about doing this? I'm completely new to rails (and sql), so may have done something naive.

  Any help would be great.

  解决方案

  So am I right in saying you have 3 models

  • User (id, name)
  • PositiveConnection (user_a_id, user_b_id)
  • NegativeConnection (user_a_id, user_b_id)

  Or something of that sort.

  I think you just want 2 models and for convenience I'm going to rename the relations as "from_user" and "to_user"

  • User (id, name)
  • Connection (value:integer, from_user_id, to_user_id)

  Where value is -1 for a negative and +1 for a positive.

  Now we can have do something like (note: you need to sort out the exact syntax, like :foreign_key, and :source, and stuff)

  class User
  
    has_many :connections, :foreign_key => "from_user_id"
    has_many :connected_users, :through => :connections, :source => :to_user
  
    def positive_connections
      connections.where(:value => 1)
    end
  
    def negative_connections
      ...
    end
  
  end
  

  But we also now have a framework to create a complex sql query (again you need to fill in the blanks... but something like)

  class User
  
    def positive_connected_users
      connected_users.joins(:connections).group("from_user_id").having("SUM(connections.value) > 0")
    end
  
  end
  

  this isn't quite going to work but is kind of pseudo code for a real solution

  (it might be better to think in pure sql terms)

  SELECT users.* FROM users
  INNER JOIN connections ON to_user_id = users.id
  WHERE  from_user_id = #{user.id}
  HAVING SUM(connections.value) > 0
  

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