title: Swift: Add operations to DispatchQueue/OperationQueue but launch the queue later
body: <p>I have data packets coming in but in rare occurrences, the object to handle them isn't ready yet. What I'm doing at the moment is</p>
  
  <ul>
  <li>adding the data to an array</li>
  <li>have a <code>while (true)</code> loop checking for the objects state</li>
  <li>if the object is ready, pop the array members onto the object</li>
  </ul>
  
  <p>This works but it's pretty ugly. What I was thinking was to add the pending operations to an OperationQueue and then launch the process once the handling object is ready.</p>
  
  <p>However, I cannot find any feature that allows me to have the operations "on hold" until I tell them to start going.</p>
  
  <p>What can I do about that?</p>