How to make dispatch_async nil out block

Question

I was reading this: does dispatch_async copy internal blocks

and I want to know how to get dispatch-async to nil out the block it copied onto the heap so that the block can be garbage collected.

Ok, so on the local stack, I create my block:

MyBlock aBlock = ^{
        for (int i = 0; i < 10; i++) {
            NSLog(@"holder is: %p, holder.block is %p", holder, holder.block);
            sleep(1);
        }
    };

dispatch_queue_t queue = dispatch_queue_create(NULL, DISPATCH_QUEUE_SERIAL);
dispatch_async(queue, aBlock);

sleep(2);     // give the queue some time to start executing the block

The block keeps executing simply because it is the block on the heap that is copied by dispatch_async. This is all expected behavior.

So my question is....is there a way to explicitly make this block on the heap be destroyed ?

Or will ARC memory manage that block for me from the heap when the dispatch_async has finished executing, and I personally can't do anything about it ?

Thank you!

Answer 1

For your updated question, you don't need to nil anything. The block on the heap is just like any other reference counted object. Your scope has a strong reference to it for the duration of the scope of the variable aBlock. And the asynchronous dispatch mechanism holds a strong reference to it until it has executed. When there are no strong references to it anymore, it is deallocated.