NSURLSession: uploading assets with background transfer
问题 What's the best approach to use background transfer to upload assets from gallery? Seems like uploadTaskWithRequest:fromData: doesn't work with NSURLSession created with backgroundSessionConfiguration since it causes an exception: "Terminating app due to uncaught exception 'NSGenericException', reason: 'Upload tasks in background sessions must be from a file". Judging from the exception description background transfer shouldn't work with streamed upload tasks too. Fair enough.