title: IOS How to download only proper images in a Collection View?
body: <p>To limit images downloads only to those that are useful (I mean when you're not scrolling too fast), Im using NSURLSessionTask in <code>tableView:willDisplayCell:forRowAtIndexPath:</code> and then cancelling it in <code>tableView:didEndDisplayingCell:forRowAtIndexPath:</code> in order not to keep downloading for useless Table View cells.</p>
  
  <p>I didn't notice such an interesting method as <code>collectionView:didEndDisplayingCell:forRowAtIndexPath:</code> for a Collection View.
  Is there a specific way to abort useless downloads in the same way for a Collection View without using external APIs, please ?</p>
  
  <p>Thanks in advance for your returns.  :o)</p>