NSURLSession use in Objective-C with Delegate or with Blocks

nsurlsession.objc

- (void)downloadSomethingWithoutDelegate{
    NSURL *url = [NSURL URLWithString:@"https://vignette.wikia.nocookie.net/vsbattles/images/4/4a/Askeladd.jpg"];
    NSURLSessionDownloadTask *downloadTask = [[NSURLSession sharedSession] downloadTaskWithURL:url completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) {
                                                       // 4
                                                       downloadedImage = [UIImage imageWithData:[NSData dataWithContentsOfURL:location]];
                                                   }];
    

    //3
    //[downloadTask resume];
}



- (void)downloadSomethingWithADelegate{
    // Create a session
    NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfiguration delegate:self delegateQueue:nil];
    NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithURL:[NSURL URLWithString:@"http://google.com/sample.jpg"]];
    [downloadTask resume];
}


- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location {
    NSData *data = [NSData dataWithContentsOfURL:location];
    
    // To do something on the main thread, like update the UI
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.progressView setHidden:YES];
        [self.imageView setImage:[UIImage imageWithData:data]];
    });
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes {
    
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
    float progress = (double)totalBytesWritten / (double)totalBytesExpectedToWrite;
    
    // To do something on the main thread, like update the UI
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.progressView setProgress:progress];
    });
}