title: How do I use NSOperationQueue with NSURLSession?
body: <p>I'm trying to build a bulk image downloader, where images can be added to a queue on the fly to be downloaded, and I can find out the progress and when they're done downloading.</p>
  
  <p>Through my reading it seems like <code>NSOperationQueue</code> for the queue functionality and <code>NSURLSession</code> for the network functionality seems like my best bet, but I'm confused as to how to use the two in tandem.</p>
  
  <p>I know I add instances of <code>NSOperation</code> to the <code>NSOperationQueue</code> and they get queued. And it seems I create a download task with <code>NSURLSessionDownloadTask</code>, and multiple if I need multiple tasks, but I'm not sure how I put the two together.</p>
  
  <p><code>NSURLSessionDownloadTaskDelegate</code> seems to have all the information I need for download progress and completion notifications, but I also need to be able to stop a specific download, stop all the downloads, and deal with the data I get back from the download.</p>