CODEWITHSUNDEEP
iosobjective-cnsthreaddispatch
ronan
ronan

Reputation: 1611

dispatch_async handle event

I know dispatch_async can handle thread.

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{  
    // handle things that takes a long time
    dispatch_async(dispatch_get_main_queue(), ^{  
        // update UI 
    });  
});

But How can I cancel it the thread?

For example:

I have two viewcontrollers- AViewController and BViewController, A->present B, and a button to dismiss B.

I'll do myMethod in BViewController, the things is I want to dismiss B when exec myMethod, so I use dispatch_async, it did dismiss from B to A. but after going back to AViewController, here comes the audio.

How can I stop the myMethod after dismiss method exec immediately?

- (void)myMethod {
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{  
        // handles thing A
        // play a audio
        dispatch_async(dispatch_get_main_queue(), ^{  
            // update UI 
        });  
    }); 
}

Upvotes: 1

Views: 132

Answers (1)

TotoroTotoro
TotoroTotoro

Reputation: 17612

What you need for this is not GCD and dispatch_async, but an NSOperation. It is a high-level wrapper around GCD that allows you to have references to your async operations, check their status, cancel them, etc.

I recommend using a very handy subclass named NSBlockOperation. You should keep a reference to your operation in your class, and if you need to cancel it, just call [self.myOperation cancel].

Upvotes: 2

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