NSNotificationQueue多线程

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setFrame:CGRectMake(0, 0, 400, 60)];
[button addTarget:self action:@selector(buttonDown) forControlEvents:UIControlEventTouchUpInside];
[button setTitle:@"Post Notification" forState:UIControlStateNormal];
[self.view addSubview:button];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(actionNotification:)
name:kNotificationName object:nil];
});
}
- (void) actionNotification: (NSNotification*)notification
{
NSString* message = notification.object;
NSLog(@"%@",message);
sleep(5);
NSLog(@"Action Notification Finish");
}
- (void)buttonDown
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSNotification *notification = [NSNotification notificationWithName:kNotificationName
object:@"object"];
[[NSNotificationQueue defaultQueue] enqueueNotification:notification
postingStyle:NSPostASAP];
});
NSLog(@"buttonDown");
}
打印信息如下：

2015-03-17 18:47:20.131 AppTest[19507:206469] buttonDown
也就是说，观察者们和poster有可能都在不同的子线程中，这样观察者们就收不到通知事件，
这里有个解决方法是把通知队列放主线程中去；
还有个解决方法就是把NSPostASAP改为NSPostNow。