如何从KVO方法observeValueForKeyPath:ofObject:change:context:中的更改字典中获取int值? [英] How can I get int values from the change dictionary in KVO method observeValueForKeyPath:ofObject:change:context:?

问题描述

我通过像这样调用以下方法来观察AVPlayer的rate属性中的变化:

I am observing changes in the rate property of an AVPlayer by calling the following method on it like so:

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

因此，我从observeValueForKeyPath:ofObject:change:context:获得的change词典是:

The change dictionary I get back from observeValueForKeyPath:ofObject:change:context: is therefore:

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

我检查了每个值的类，结果是__NSCFNumber.但是，当我尝试将[change objectForKey:@"new"]或[change objectForKey:@"old"]转换为int，NSInteger，NSNumber甚至尝试使用NSString等时，它适用于旧"，但是却为我提供了新"的解析错误:

I checked the class of each value, and it turns out to be __NSCFNumber. However, when I try to convert [change objectForKey:@"new"] or [change objectForKey:@"old"] into an int, NSInteger, NSNumber, even tried NSString, etc, it works for "old", but it gives me a parsing error for the "new":

error: expected a type
error: 1 errors parsing expression

我真的需要比较它们，我无法弄清楚.这可能是iOS中的错误吗?

I really need to compare them, and I can't figure it out. Could this be a bug in iOS?

推荐答案

目标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;
}

迅速

   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
        }
    }

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