equivalent of waitUntilAllOperationsAreFinished

Question

i want to show an alertview while other thread(in other thread there is text to speech). in short words, i want to call two methods at same time and also want them that both "work" at same time.

but in my case, i am starting alertView, the screen is dimmed and without alertview, the other thread gets started. after the other thread is ready, i am getting the blue alertview:

Here is the code and my question is: What is the equivalent to waitUntilAllOperationsAreFinished..?

dispatch_async(dispatch_get_main_queue(), ^{
        [self alertWhileTTS];
    });

    [[self view] setNeedsDisplay];
    [self synthesizeInBackground];
    [queue waitUntilAllOperationsAreFinished];
    [self setIsSpeaking: false];
    [[self view] setNeedsDisplay];

Also see this post: How to multithred correctly? UIAlertView is not displayed, only gray screen

Answer 1

this solves my problem:

[self performSelectorOnMainThread:@selector(alertWhileTTS) withObject:nil waitUntilDone:YES];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, (unsigned long)NULL), ^(void) {
        [[self view] setNeedsDisplay];
        [self synthesizeInBackground];
        [queue waitUntilAllOperationsAreFinished];
        [self setIsSpeaking: false];
        [[self view] setNeedsDisplay];

    });