How can I check that an NSData blob is valid as resumeData for an NSURLSessionDownloadTask?

Question

I have an app that\'s using background downloads with the new NSURLSession APIs. When a download cancels or fails in such a way that NSURLSessionDownloadT

Answer 1

This is the workaround suggested by Apple:

- (BOOL)__isValidResumeData:(NSData *)data{
    if (!data || [data length] < 1) return NO;

    NSError *error;
    NSDictionary *resumeDictionary = [NSPropertyListSerialization propertyListWithData:data options:NSPropertyListImmutable format:NULL error:&error];
    if (!resumeDictionary || error) return NO;

    NSString *localFilePath = [resumeDictionary objectForKey:@"NSURLSessionResumeInfoLocalPath"];
    if ([localFilePath length] < 1) return NO;

    return [[NSFileManager defaultManager] fileExistsAtPath:localFilePath];
}

Edit (iOS 7.1 is not NDA'd anymore): I got this from a Twitter exchange with an Apple engineer, he suggested what to do, and I wrote the above implementation