KVO的使用(键值监听)

Key-Value Observing  键值监听。

stockForKVO = [[StockData alloc] init];      [stockForKVO setValue:@"searph" forKey:@"stockName"];      [stockForKVO setValue:@"10.0" forKey:@"price"];          [stockForKVO addObserver:self forKeyPath:@"price" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL]; 

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{    if([keyPath isEqualToString:@"price"])    {        myLabel.text = [stockForKVO valueForKey:@"price"];    }}

- (void)dealloc{    [super dealloc];    [stockForKVO removeObserver:self forKeyPath:@"price"];    [stockForKVO release];}