title: How to change CSS class after Ajax request in Angular
body: <p>I can't figure out what I'm supposed to use in the following situation:</p>
  
  <ul>
  <li>The template list a bunch of photos </li>
  <li>Each photo element has a ng-click
  event that marks the photo as selected and sends an Ajax request to
  save the photo</li>
  <li>When the save happens, I want to update the class of
  the photo element to show it as selected</li>
  </ul>
  
  <p>I have a call tie to my ng-class that works when the page loads, but it is called too early when the user clicks. It should be called after the save.</p>
  
  <p>How do I do this?</p>
  
  <p>Thanks a lot.</p>