How to dispatch_group_wait for dispatch_group_async inside an asynchronous block

Question

I have code that looks something like this:

[SVProgressHUD show];
[imageGenerator generateCGImagesAsynchronouslyForTimes:times
                completionHand         


        

Answer 1

Think of this method as a static counter available to threads, so when you enter a group the counter increments, and when that block returns, decrements...

When that counter is 0, it will call a block to invoke

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_t group = dispatch_group_create();

while(someCondition)
{
    dispatch_group_enter(group);
   [SomeClassThatLoadsOffTheInternet getMyImages:^{

        // do something with these.
        dispatch_group_leave(group);

    });
}

dispatch_group_notify(group, queue, ^{
    // do something when all images have loaded
});

Is that what you were thinking of?