Swift：哪个 class 拥有 NSObject.addObserver（...选项：.New）中使用的 .New 属性？

Question

Swift 中 KVO 的当前最佳实践在 this SO post 中有详细记录，看起来像这样：

someObject.addObserver( self, forKeyPath: "someProperty", options: .New, 
    context: &self.someContext )

我想通过将其封装在 ObserversManager（比如说）class 中来简化内存管理问题，所以我可以这样做：

func observe ( observed: NSObject, observer: NSObject, keyPath: String, 
    context: Int )
{
    observed.addObserver( observer, forKeyPath: keyPath, options: .New, 
        context: context ) { ... }
}

func removeObserversByObserver ( observer: NSObject ) { ... }
func removeAllObservers () { ... }

问题是上面的func observer抛出了下面的编译时错误，我目前无力修复，因为官方文档没有详细说明问题的答案。 Could not find member 'New'

Answer 1

错误消息具有误导性。问题是 context: 参数是一个 pointer，而不是 Int:

func observe ( observed: NSObject, observer: NSObject, keyPath: String,
    context: UnsafeMutablePointer<Void> )
{
    observed.addObserver(observer, forKeyPath: keyPath, options: .New,
                         context: context)
}

Swift：哪个 class 拥有 NSObject.addObserver（...选项：.New）中使用的 .New 属性？

Swift: which class owns the .New property used in NSObject.addObserver( ... options: .New )?

swift

key-value-observing

nsobject

throw

addobserver