[IOS学习笔记]KVO

//属性
@property(nonatomic) BOOL isFinished;

//注册监听
 [self addObserver:self forKeyPath:@"isFinished" options:0 context:NULL];

//响应变更事件
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqualToString:@"isFinished"]) {
        NSLog(@"changeeddd");
    } else {
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

//变更属性数值
[button addTarget:self action:@selector(changeFinished:) forControlEvents:UIControlEventTouchUpInside];

-(void)changeFinished:(id)sender {
//自动通知
    [self setValue:[NSNumber numberWithBool:YES] forKey:@"isFinished"];

}

注册监听器参数 options

NSKeyValueObservingOptionNew 表示属性未改变​之前的值；

NSKeyValueObservingOptionOld 表示属性改变后的值；​

移除观察者：

[subject removeObserver:observer forKeyPath:@"name"]; 

KVO相当于JAVA:

account.setListener(new MyListener(){

    inspector.method();

});

但是不需要和JAVA一样声明一个MyListener接口，也不需要在account类中新建一个setListeber(MyListener listener);的方法，所以更灵活,但是变更属性时不能简单赋值！