将GCD转换为NSOperationqueue

Question

如果在使用NSOperation时可以取消任务，而如果我使用GCD，那么一旦我将任务分配到队列然后我们无法取消它，因此我想知道我怎么能转换我在GCD到NSOperation

中的以下实施

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];