title: AFNetworking 2.0 with NSProgress - Multiple Files
body: <p>I'm interested in replacing some old AFNetworking 1.0 code with 2.0 using NSProgress. Here is a sketch of what I'm thinking of...</p>
  
  <pre><code>NSProgress *overallProgress = [NSProgress progressWithTotalUnitCount:[requests count]];
  for (NSURLRequest *request in requests) {
     [overallProgress becomeCurrentWithPendingUnitCount:1];
     [self downloadTask:request];
     [overallProgress resignCurrent];
  }
  
  - (void)downloadTaskWithRequest:(NSURLRequest *)request
  {
     NSProgress *progress = nil;
     NSURLSessionDownloadTask *task = [self.sessionManager downloadTaskWithRequest:request progress:&amp;progress destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
     } completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
     }];
  }
  </code></pre>
  
  <p>I've read several posts on this and I'm having trouble composing the sub-tasks progress with the overallProgress. Getting progress back for a single file works, but trying to compose NSProgress tasks under and umbrella task eludes me.</p>
  
  <p>How can I create an overall task with N pieces and then have each file as its download update the overall task?</p>