title: iOS QLPreviewController load file from remote server URL
body: <p>What is approach should be used while loading files from remote server on QLPreviewController?
  When should we download files using my server API to load them on QLPreviewController. 
  I am adding QLPreviewController as subview to my current view.
  I can use datasource method to make call to download file from server.</p>
  
  <pre><code>- (id&lt;QLPreviewItem&gt;)previewController:(QLPreviewController *)controller previewItemAtIndex:(NSInteger)index
  </code></pre>
  
  <p>But once file is downloaded i need to reload QLPreviewController, where this should be done
  For images i would like to image gallery view so that swipe to view images downloaded from server.
  Can anyone point me to any tutorial to load images from remote server URL</p>