KVO监听者

监听者模式方便的监听所需要的值得变化

@implementation ViewController

- (IBAction)Buton:(id)sender {

    

    self.view.backgroundColor=[UIColor redColor];

    

}

 

- (void)viewDidLoad {

    

    [super viewDidLoad];

    self.model=[[Model alloc]init];

    //第一个参数是 被监听者

    //第二个参数是  监听者

    //第三个参数是  监听内容

    //第四个参数是   监听的状态变化

    //

     [self.view addObserver:self forKeyPath:@"backgroundColor" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:nil];

    [self.model addObserver:self forKeyPath:@"age" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:nil];

    self.model.age=@"18";

    self.model.age=@"12";

    // Do any additional setup after loading the view, typically from a nib.

}

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{

    if ([keyPath isEqualToString:@"age"]) {

        NSLog(@"01%@",keyPath);

        NSLog(@"02%@",change);

        NSLog(@"03%@",object);

        NSLog(@"04%@",context);

    }

}