title: NSPredicate Sort Array and Order DESC
body: <p>I have an <code>NSMutableArray</code> containing <code>TBPosts</code> that I would like to filter in descending order according to the <code>commentsCount</code> and <code>likesCount</code> of the <code>TBPost</code>.</p>
  
  <p>Initially, the first object in the filtered array will be the object with the largest number of comments and likes, which can be worked out by adding the two together. So I tried the following query and receive an Unable to Parse error. Please can you tell me where I am going wrong?</p>
  
  <pre><code>[posts filterUsingPredicate:[NSPredicate predicateWithFormat:@"post.commentsCount + post.likesCount DESC"]];
  </code></pre>