GCD: How to remove waiting tasks from serial queue?

Question

First I create a serial queue like this

static dispatch_queue_t queue = dispatch_queue_create(\"myQueue\", DISPATCH_QUEUE_SERIAL);

then, at som

Answer 1

The way you handle this is to use an ivar that indicates to the queued blocks they should just return:

^{
  if(!canceled) {
    ... do work
  }
}

You don't need to use a simple boolean either - you can make this more complex - but the general idea is to use one or more ivars that the block queries before doing anything.

I use this technique (but did not invent it) with great success.