title: Multiple Delegates in iOS
body: <p>I am making an object that goes to download stuff for all of my view controllers. The object is singleton instance and has a callback method with received data once the download is completed. It also has a delegate property so that it knows which object to call back to after the download is done.</p>
  
  <p>There are multiple controllers that use this shared instance, and my question is how to call back to the correct view controller that requested the download.</p>
  
  <p>My approach is to use delegation, but the problem is that since other view controllers are also its delegate, the download object could call back to every object and this will be hard to track.</p>