【IOS学习】KVO的使用，demo

KVO nsobject类实现NSKeyValueCoding / NSKeyValueObserving非正式协议

本质上定义了一套让我们去遵守和实现的方法 KVO的使用

KVO的使用

//添加监听
     = [[Book alloc]init];
    [_abook addObserver:self forKeyPath:@"price" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];

//实现监听
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqual:@"price"]) {
        NSLog(@"old price: %@",[change objectForKey:@"old"]);
        NSLog(@"new price: %@",[change objectForKey:@"new"]);
    }
}

-(void)dealloc
{
    //移除监听
    [_abook removeObserver:self forKeyPath:@"price"];
}

//触发监听
    NSDictionary *newBookPropertiesDictionary=[NSDictionary dictionaryWithObjectsAndKeys:
                                               @"book name",@"name",
                                               @"20.5",@"price",nil];
    [ setValuesForKeysWithDictionary:newBookPropertiesDictionary];
    
    [ setValue:@"34.0" forKey:@"price"];

Demo 下载地址：/caigee/iosdev_sample

下的KVOdemo

厚吾（/mangosnow）

本文遵循“署名-非商业用途-保持一致”创作公用协议