title: NSPredicate fails with BOOL
body: <p>I try to filter an array of objects that have <code>@property BOOL</code> missed
  depending on the value of this property</p>
  
  <p>I defined:</p>
  
  <pre><code>NSPredicate *missedInvitationsPredicate = [NSPredicate predicateWithBlock: ^BOOL(CRGQuizInvitation* invitation, NSDictionary *bind){
      return invitation.missed == YES;
  }];
  </code></pre>
  
  <p>but it fails. I tried a lot of things like using predicateWithFormat, one equal sign and many others. at the end I solved it by converting the <code>BOOL</code> to <code>NSNumber</code>, but I still want to know what's wrong with that.</p>