Download on image from another thread(GCD)

dispatch_queue_t downloadQueue = dispatch_queue_create("image", NULL);

    dispatch_async(downloadQueue, ^{

        NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://blogs-images.forbes.com/jasonevangelho/files/2013/01/iphone5.jpeg"]];

        dispatch_async(dispatch_get_main_queue(), ^{

            UIImage *image = [UIImage imageWithData:imageData];

            imageView.image = image;

            imageView.frame = CGRectMake(0, 0, image.size.width, image.size.height);

            scrollView.contentSize = image.size;

        });

    });

    dispatch_release(downloadQueue);

Downloading a file from url and saving to resources on iPhone

- (void)viewDidLoad
{
    [super viewDidLoad];
   self.fileData = [NSMutableData data];

    NSString *file = [NSString stringWithFormat:@"http://en.wikipedia.org/wiki/Text_file"];
    NSURL *fileURL = [NSURL URLWithString:file];

    NSURLRequest *req = [NSURLRequest requestWithURL:fileURL];
    NSURLConnection *conn = [NSURLConnection connectionWithRequest:req delegate:self];  
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [self.fileData setLength:0];
    self.totalFileSize = [NSNumber numberWithLongLong:[response expectedContentLength]];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
        [self.fileData appendData:data];        
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSArray *dirArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,    NSUserDomainMask, YES);
    NSLog(@"%@", [dirArray objectAtIndex:0]);

    NSString *path = [NSString stringWithFormat:@"%@/blah.text", [dirArray objectAtIndex:0]];

    if ([self.fileData writeToFile:path options:NSAtomicWrite error:nil] == NO) {
        NSLog(@"writeToFile error");
    }
    else {
        NSLog(@"Written!");
    }
}