title: Startup lag on iOS
body: <p>when users launch my app, I request from websocket the list of session of a chat system.
  When the websocket responds to the request, I parse the results to build the session and then i parse the message and add them to the messageList of every Session, like this:</p>
  
  <pre><code>    for (NSDictionary *session in sessions) {
        for (NSDictionary *message in messages) {
  
          ChatMessage *message = [[ChatMessage alloc] init];
          [listOfMessages addObject:message];
  
         } 
      }
  </code></pre>
  
  <p>This cause a one second lag at startup. How can I reduce It?</p>
  
  <p>EDIT: It tooks the phone's CPU at 100% for some seconds, that's the problem, not a network one because I have all the JSON ready on ad array.</p>