Convert GCD to NSOperationqueue

Question

The task can be cancelled if while using NSOperation whereas if I use GCD, then once I assign the task to queue then we are not able to cancel it, therefore I wonder how could I convert my following implementation in GCD to NSOperation

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^(void) {
     [self addAllImages];
      dispatch_sync(dispatch_get_main_queue(), ^(void) {
             [self pageControlSetUp];
             self.fullScreenImageView.hidden = YES;
       });
 })

Answer 1

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
  [self addAllImages];
  dispatch_sync(dispatch_get_main_queue(), ^(void) {
    [self pageControlSetUp];
    self.fullScreenImageView.hidden = YES;
  });
}];


[queue addOperation:operation];


//cancel operation
[operation cancel];

//or to cancell all operations
[queue cancelAllOperations];