gistfile1.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    
    NSObject* ob = [NSObject new];
    dispatch_async(dispatch_get_main_queue(), ^{
        NSLog(@"A: %d",[ob retainCount]);
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"B: %d",[ob retainCount]);
        });
        NSLog(@"C: %d",[ob retainCount]);
    });
    NSLog(@"D: %d",[ob retainCount]);
}