How to work with large file uploads in ios?

Question

My app requires upload of video files from users phone which will then be processed on server. THe problem is the size of the file can go to 200 MB plus and the user won't keep the application open to wait for the file to upload. Since apple doesn't allow apps to run in background for more than a limited time. How can I ensure that my files are uploaded. I am using afnetworking to set up an upload task as given by ios 7 library.

Please if anyone can point me in the right direction or have any solution it would be greatly appreciated. I have banged my head on this for too long. Thanks.

        NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];


    [manager setTaskDidSendBodyDataBlock:^(NSURLSession *session,NSURLSessionTask *task ,int64_t bytesSent, int64_t totalBytesSent,int64_t totalBytesExpectedToSend){
        CGFloat progress = ((CGFloat)totalBytesSent / (CGFloat)sensize);

       NSLog(@"Uploading files %lld  -- > %lld",totalBytesSent,totalBytesExpectedToSend);
        [self.delegate showingProgress:progress forIndex:ind];
    }];



    dataTask = [manager uploadTaskWithStreamedRequest:request progress:nil completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) {
        if (error) {
            NSLog(@"Error: %@", error);
        } else {

        }

       }];

My request is a normal multipart form request.

Answer 1

Use:

NSURLSessionConfiguration:backgroundSessionConfiguration:

instead of

NSURLSessionConfiguration:defaultSessionConfiguration

From the NSURLSessionConfiguration:backgroundSessionConfiguration: documentation:

Upload and download tasks in background sessions are performed by an external daemon instead of by the app itself. As a result, the transfers continue in the background even if the app is suspended, exits, or crashes.

So in your case, change:

NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];

to:

NSString *appID = [[NSBundle mainBundle] bundleIdentifier];
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration backgroundSessionConfiguration:appID];

Implementing application:handleEventsForBackgroundURLSession:completionHandler: on your app delegate will allow your app to be woken up (ie. un-suspended or un-terminated in background mode) when an upload has completed (whether it has completed successfully or not).

Don't get confused with Background Fetching. You don't need it. Background Fetching simply wakes you app up to periodically give your app the chance to fetch small amounts of content regularly. It may however, be useful for restarting failed "background-mode" uploads periodically.

Answer 2

You should use a background session configuration instead if a default session configuration. This ensures that your data transfer will continue in the background once the user has exited your app.

Of course, this is correct as long as the user has background fetching enabled for your app in the Settings app of the device.

Be sure to enable the Background fetch capability on your project settings:

_{(source: migueldiazrubio.com)}

_{(source: migueldiazrubio.com)}

Then implement the application:handleEventsForBackgroundURLSession:completionHandler: in your App Delegate to be informed when the data transfer ends and do whatever you need to do (UI update…) inside your app with the received/sent file. Don't forget to call the completionHandler to inform the system that you have ended your tasks. iOS then will take a screenshot of the active screen of your app and update the one in the iOS 7 multitasking screen.