Objective C wait until an asynch task has been processed

Question

In my code, I am running a local server (CocoaHTTPServer). When the server receives a request, it creates a thread and passes control to a certain method ( - (NSObject<

Answer 1

You can use semaphore to block execution of the current queue until another one returns.
The basic pattern is:

dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
[assetsLibrary enumerateAssetsUsingBlock^(ALAsset *result, NSUInteger index, BOOL *stop):^{
    ...
    dispatch_semaphore_signal(semaphore);
}];
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
dispatch_release(semaphore);

You can find a full example of this method in Apple's MTAudioProcessingTap Xcode Project: https://developer.apple.com/library/ios/samplecode/AudioTapProcessor
The relevant lines start at MYViewController.m:86