ios - 如何从 KVO 方法 observeValueForKeyPath :ofObject:change:context:? 中的更改字典中获取 int 值

Question

我通过调用以下方法来观察 AVPlayer 的 rate 属性的变化:

addObserver:sharedPlayerManagerInstance
 forKeyPath:@"rate"
    options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld
    context:0]; 

因此，我从 observeValueForKeyPath:ofObject:change:context: 返回的 change 字典是:

change = { kind: 1,
            new: 1,
            old: 0 }

我查看了每个值的类，原来是__NSCFNumber。但是，当我尝试将 [change objectForKey:@"new"] 或 [change objectForKey:@"old"] 转换为 int、NSInteger、NSNumber 时，甚至尝试过NSString 等，它适用于“旧”，但它给了我一个"new"的解析错误:

error: expected a type
error: 1 errors parsing expression

我真的需要比较它们，我想不通。这可能是 iOS 中的错误吗？

Answer 1

objective-c

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
NSNumber * newValue = [change objectForKey:NSKeyValueChangeNewKey];
NSInteger integerValue = newValue.integerValue;
int intValue = newValue.intValue;
}

swift

   override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer<Void>) {
        if let newValue = change[NSKeyValueChangeNewKey] as? NSNumber{
            let intvalue = newValue.intValue //To int
        }
    }