NSURLDomainErrorDomain error -999 when app terminate with NSURLSession

I have big trouble with NSURLSession when i'll terminate the App. I have downloaded the apple sample: https://developer.apple.com/library/ios/samplecode/SimpleBackgroundTransfer/Introduction/Intro.html

on Apple reference.

When i start download the file download correctly. When i enter in background the download continues to. When i terminate the application and i restart the app the application enter in:

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error

And i catch this error:

The operation couldn't be completed. (NSURLErrorDomain error -999.)

It seems that i cannot restore download when app has been terminated. It's correct?For proceed with download i must leave application active in background?

Thank you Andrea

Solution

i insert this new lines of code:

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
    BLog();

    NSInteger errorReasonNum = [[error.userInfo objectForKey:@"NSURLErrorBackgroundTaskCancelledReasonKey"] integerValue];

    if([error.userInfo objectForKey:@"NSURLErrorBackgroundTaskCancelledReasonKey"] &&
       (errorReasonNum == NSURLErrorCancelledReasonUserForceQuitApplication ||
        errorReasonNum == NSURLErrorCancelledReasonBackgroundUpdatesDisabled))
    {
        NSData *resumeData = error.userInfo[NSURLSessionDownloadTaskResumeData];
        if (resumeData) {
            // resume
            NSURL *downloadURL = [NSURL URLWithString:DownloadURLString];
            NSURLRequest *request = [NSURLRequest requestWithURL:downloadURL];
            if (!self.downloadTask) {
                self.downloadTask = [self.session downloadTaskWithRequest:request];
                         }

            [self.downloadTask resume];
            if (!_session){
               [[_session downloadTaskWithResumeData:resumeData]resume];
                                         }
        }
    }
}

It catch NSURLErrorCancelledReasonUserForceQuitApplication but when the application try to [[_session downloadTaskWithResumeData:resumeData]resume]

reenter again in:

(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {

and give me again -999 error.