using dispatch_sync in Grand Central Dispatch

Question

Can anyone explain with really clear use cases what the purpose of dispatch_sync in GCD is for? I can\'t understand where and why I would have to u

Answer 1

dispatch_sync is mainly used inside dispatch_async block to perform some operations on main thread(like update ui).

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    //Update UI in main thread
    dispatch_sync(dispatch_get_main_queue(), ^{
      self.view.backgroundColor = color;
    });
});