NSURLSession委托跨类拆分 - NSURLSession，NSURLUploadTask，NSURLDownloadTask

I'm in the process of creating an upload/download media feature for my app. I had the queue working fine for uploads but when I added downloads and the requisite download delegates the upload delegate was called event though the task was to download. My initial class structure was a singleton QueueController that had the NSURLSession and delegates (but not download) along with a TransferModel that could hold either the upload or download. When I tried to add downloads the callbacks were not working right so I moved to put the transfer related delegates in two sub classes TransferUploadModel and TransferDownloadModel but now my delegates are not firing. I'm in the process of creating an upload/downlo