title: How to put image into AutoPurgingImageCache after af_setImageWithURL completed?
body: <p>I want to use <code>imageView.af_setImageWithURL(URL)</code> together with the <em>AutoPurgingImageCache</em> from <a href="https://github.com/Alamofire/AlamofireImage" rel="nofollow">AlamofireImage</a>.</p>
  
  <p>How can I be informed that <code>af_setImageWithURL</code> fetched the image, so I can put it into my cache? Because this is done in Background.</p>
  
  <p>I'd prefer something like: <code>imageView.af_imageFromCache(URL)</code> which sets the image from cache if it is already in there or otherwise downloads async, then sets the image and saves it in the cache.</p>