add observer的两个用法

[[NSNotificationCenter defaultCenter]postNotificationName:NOTIFICATIONNAME object:nil userInfo:userinfo];//userinfo是个dictionary

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(selectorName:) name:NOTIFICATIONNAME object:nil];
//收到广播要做的事件
-(void)selectorName:(NSNotification *)notification{
NSDictionary *dic= [notification userInfo];
}

per= [[Person alloc] init];  //per是全局的
[per setValue:@"annie" forKey:@"name"];
[per setValue:@"20" forKey:@"age"];
[per addObserver:self forKeyPath:@"age" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];
//此处的self是谁来监听per的变化，谁来监听在谁那里调回调方法

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{  //object为per ，keyPath为age
if([keyPath isEqualToString:@"age"])
{
//do something
}
}

- (void)dealloc
{
[per removeObserver:self forKeyPath:@"age"]; //kvo的
[NSNotificationCenter defaultCenter]removeObserver:self]; //广播的
[per release];
//[super dealloc];
}