title: Parse ios wherekey using objectid
body: <p>In my "<code>Message</code>" table in Parse I have a field called conversation, which is a <code>pointer</code> to a <code>Conversation</code> (another table in my database).</p>
  
  <p>To query for a <code>Message</code>, can I do: </p>
  
  <pre><code>    PFQuery *messageQuery = [PFQuery queryWithClassName:@"Message"];
      [messageQuery whereKey:@"conversation" equalTo:_conversation.objectid];
      [messageQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
  
            ...
  
      }];
  </code></pre>
  
  <p>or do I have to get the actual PFObject *myConversation and use that...</p>
  
  <pre><code>    PFQuery *messageQuery = [PFQuery queryWithClassName:@"Message"];
      [messageQuery whereKey:@"conversation" equalTo:myConversation];
      [messageQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
  
            ...
  
      }];
  </code></pre>
  
  <p>It seems that #1 doesn't work, but #2 does...my question is how can I get #1 to work <strong>(i.e. use a PFObject's id to query when I have a pointer field)</strong></p>