iOS开发 ☞ NSNotification

- (void)viewDidLoad {
[super viewDidLoad];
UIButton *testBtn = [UIButton buttonWithType:UIButtonTypeCustom];
testBtn.frame = CGRectMake( 100, 100, 100, 100);
testBtn.backgroundColor = [UIColor orangeColor];
[testBtn addTarget:self action:@selector(postNoti) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:testBtn];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(test) name:@"aaaa" object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(test) name:@"aaaa" object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(test) name:@"aaaa" object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(test) name:@"aaaa" object:nil];

}
- (void)test {

NSLog(@"tttttt");
}
- (void)postNoti {

[[NSNotificationCenter defaultCenter] postNotificationName:@"aaaa" object:nil];
}

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(test) name:@"aaaa" object:nil];

[[NSNotificationCenter defaultCenter] postNotificationName:@"aaaa" object:nil];

移除观察者对aaaa通知的监听，这个方法的使用需要谨慎而行，因为如果观察者没有监听aaaa通知就会崩溃，从KVO的角度理解，就是移除对通知中心aaaa这个属性的监听，当然，self对象还可以监听通知中心别的属性
[[NSNotificationCenter defaultCenter] removeObserver:self name:@"aaaa" object:nil];
这个方法是通知中心移除self对象的监听，从KVO角度理解，self将失去对通知中心所有属性的监听。如果self对象没有监听通知中心的任何消息也不会导致崩溃.
[[NSNotificationCenter defaultCenter] removeObserver:self];