title: Ember - Understanding Inverse Relationships
body: <p>After reading through the <a href="http://emberjs.com/guides/models/defining-models/">Getting Started</a> guide on Ember's page, I'm still a bit confused what exactly an inverse relationship is, and when to define them. I understand that you will probably need to use them when defining multiple relationships of the same type, but I found the example to be very unclear. This is the sample from the docs:</p>
  
  <pre><code>var belongsTo = DS.belongsTo,
      hasMany = DS.hasMany;
  
  App.Comment = DS.Model.extend({
    onePost: belongsTo('post'),
    twoPost: belongsTo('post'),
    redPost: belongsTo('post'),
    bluePost: belongsTo('post')
  });
  
  
  App.Post = DS.Model.extend({
    comments: hasMany('comment', {
      inverse: 'redPost'
    })
  });
  </code></pre>
  
  <p>In this example, why is the <code>redPost</code> singled out as the inverse instead of one of the other kinds of posts? How does defining <code>redPost</code> as the inverse differentiate it from the rest? I also don't really understand why a comment has multiple posts at all really, just adding to my confusion.</p>