Dispatch queues: How to tell if they're running and how to stop them

Question

I\'m just playing around with GCD and I\'ve written a toy CoinFlipper app.

Here\'s the method that flips the coins:

- (void)flipCoins:(NSUInteger)nFl         


        

Answer 1

If you have a serial dispatch queue OR a concurrent dispatch queue, here is a code that can do the same thing.

BOOL __block queueIsEmpty = false;
dispatch_barrier_async (_dispatchQueue, ^{
    queueIsEmpty = true;
});

while (!queueIsEmpty) {
    int i = 0;  // NOOP instruction
}

// At this point your queue should be empty.