Repeating work on background thread with GCD and blocks

gistfile1.m

- (void)doStuff
    // Do stuff on main thread

    dispatch_async(self.queue, ^{
        // Do stuff on background thread
        // self.queue is a serial queue stored as a property on this object

        dispatch_async(dispatch_get_main_queue(), ^{
            // Do stuff on main thread
        });
                
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, self.delay * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
            // Call doStuff again on the main thread after delay
            [self doStuff];
        });
    });
}