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POClass method problem with bidirectional self-referential associations
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copied!<p>I'm trying to create an app where users ('current_user') rate the compatibility between two other users ('user1' and 'user2'). They can rate compatibility either positively or negatively: rating two users "compatible" creates two resources of the same class (a 'positive_connection' and an 'inverse_positive_connection' - for bidirectionality), and rating them "incompatible" also creates two resources('negative_connection' and 'inverse_negative_connection'). So there are models for positive_connection, negative_connection and user.</p> <p>Each rating resource belongs_to the user who created it, but also to the users connected by it. It's important to have both positive and negative ratings.</p> <p>This is my problem: on every user (<code>@user</code>) page I want to display separate lists of:</p> <ol> <li><p>users that are <code>overall_positively_connected_to(@user)</code> (i.e. <code>positive_connections.count > negative_ratings.count</code>), and </p></li> <li><p>users that are <code>overall_negatively_connected_to(@user)</code> (i.e. <code>negative_connections.count > positive_ratings.count</code>).</p></li> </ol> <p><br /> What I can't seem to do is write a <em>class</em> method that pulls out only those users who are net-rated "compatible" or "incompatible"</p> <p>From reading Michael Hartl's rails tutorial (I'm completely new to all this), I think I need to write something like this in the User model:</p> <pre><code>class User < ActiveRecord::Base def self.that_are_compatible_with User.overall_positively_connected_to(user) end . . . </code></pre> <p><br /></p> <p><strong>EDIT</strong></p> <p>Starting with absolutely no knowledge of SQL queries at all, I wrote these two class methods for finding users that are negatively and positively connected to @user (respectively):</p> <pre><code>. . . def self.with_neg_connections_to(user) joins(:negative_connections). where(:negative_connections => {:user_a_id => user}) end def self.with_pos_connections_to(user) joins(:positive_connections). where(:positive_connections => {:user_a_id => user}) end </code></pre> <p><br /></p> <p>But that's not much help. What I need is a method that gets the users <code>overall_positively_connected_to(user)</code>. I presume the method would involve two joins, and go something like this:</p> <pre><code> def self.overall_positively_connected_to(user) joins(:positive_connections).joins(:negative_connections). where((:negative_connections => {:user_a_id => user}).count > (:positive_connections => {:user_a_id => user}).count) end </code></pre> <p><br /> But here I get completely stuck: it's obviously not right. I can't find other examples like it anywhere...</p> <p>Any help whatsoever on this would be great as I have no clue when it comes to SQL queries. Let me know if more code needed. Thanks in advance!</p>

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