title: Symfony2 form collection — Show only the newest
body: <p>I have a form with a Parent (Entity) and Children (Record).
  A Parent has many children.
  So far so good.</p>
  
  <p>What I need is, that if I edit a Parent I want to show only the newest child as a form collection and not all of them.</p>
  
  <p>Right now with the creation of such I just make it like this:</p>
  
  <pre><code>$entity = new WikiEntity();
  $record = new WikiRecord();
  $entity-&gt;addWikiRecord($record);
  </code></pre>
  
  <p>And with this I have just one form collection — obviously.</p>
  
  <p>Now I am looking for a method to have only the newest Record (child) to edit and all of the older one shouldnt be there.</p>
  
  <p>Just to say what my goal is (maybe there are other solutions), I want to create something like a wiki, so everytime the Parent gets edited a new revision gets created, so I can get an older version or something. So the people don't need to see all of the versions (what form collection does) but only the newest one (which will be created each time you edit it).</p>