I have a method that I add to a GCD queue that I have created (so it's a serial queue) and then run it async. From within that block of code I make a dispatch to the main queue, when that block of code dispatched to the main queue is complete I set a BOOL flag to YES, so that I further down in my code can check if this condition is YES then I can continue to the next method. Here is the code in short:
dispatch_queue_t queue = dispatch_queue_create("ProcessSerialQueue", 0);
dispatch_async(queue, ^{
Singleton *s = [Singleton sharedInstance];
dispatch_sync(dispatch_get_main_queue(), ^{
[s processWithCompletionBlock:^{
// Process is complete
processComplete = YES;
}];
});
});
while (!processComplete) {
NSLog(@"Waiting");
}
NSLog(@"Ready for next step");
However this does not work, because dispatch_sync is never able to run the code on the main queue. Is this because I'm running a while loop on the main queue (rendering it busy)?
However if I change the implementation of the while loop to this:
while (!processComplete) {
NSLog(@"Waiting")
NSDate *date = [NSDate distantFuture];
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:date];
}
It works without a glitch. Is this an acceptable solution for this scenario? Can I do it any other preferred way? What kind of magic stuff does NSRunLoop
do? I need to understand this better.