Question

我通过调用以下方法来观察AVPlayer的#include <cstdio> void __fastcall TForm1::Button1Click(TObject *Sender) { int number; if (std::swscanf(Edit1->Text.c_str(), L"%d", &number) == 1) { // use number as needed... ShowMessage("It is a number"); } else { // not a number, do something else... ShowMessage("It is not a number"); } }属性的变化，如下所示：

rate

我从addObserver:sharedPlayerManagerInstance forKeyPath:@"rate" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:0];返回的change词典是：

observeValueForKeyPath:ofObject:change:context:

我检查了每个值的类，结果是__NSCFNumber。但是，当我尝试将change = { kind: 1, new: 1, old: 0 }或[change objectForKey:@"new"]转换为int，NSInteger，NSNumber，甚至尝试过NSString等时，它适用于＆＃34; old＆＃34;，但它给了我一个解析＆＃34; new＆＃34;：

的错误

[change objectForKey:@"old"]

我真的需要比较它们，我无法弄明白。这可能是iOS中的错误吗？

Answer 1

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;
}

夫特

   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
        }
    }

Answer 2

斯威夫特3：

if let newValue = change?[NSKeyValueChangeKey.newKey] as? NSNumber {
     // Do stuff
}

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

2 个答案: