// 1.键-值观察
// 2.它提供一种机制，当指定的对象的属性被修改后，则对象就会接受到通知。
// 3.符合KVC（Key-ValuedCoding）机制的对象才可以使用KVO
// 4.实现过程
// ①注册，指定被观察者
// ②实现回调方法
// ③移除观察
- (void)viewDidLoad
{ [super viewDidLoad];
// Do any additional setup after loading the view from its nib.
// 实例化一个观察者对象
self.stockForKVO = [[StockData alloc] init];
// 初始化
[self.stockForKVO setValue:@"searph" forKey:@"stockName"];// KVC
[self.stockForKVO setValue:@"10.0" forKey:@"price"];// KVC
// 监听并显示在 lable 里 - 注册观察者
[self.stockForKVO addObserver:self forKeyPath:@"price" options:NSKeyValueObservingOptionNew context:nil];
self.myLable.textColor = [UIColor redColor];
self.myLable.text = [self.stockForKVO valueForKey:@"price"];
// 创建 button 按钮
UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setFrame:CGRectMake(90, 150, 140, 42)];
[button setTitle:@"按钮" forState:UIControlStateNormal];
[button addTarget:self action:@selector(buttonAction) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];
}// button响应方法- (void)buttonAction
{ [self.stockForKVO setValue:@"20.0" forKey:@"price"];
}// 回调方法- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{ if ([keyPath isEqualToString:@"price"])
{
self.myLable.text = [self.stockForKVO valueForKey:@"price"];
}
}- (void)dealloc
{ // 移除观察者
[self.stockForKVO removeObserver:self forKeyPath:@"price"];
}