swift4 - 使用Swift 4's KVO “observe”而不是addObserver出现问题

Question

我在正确使用新的KVO语法时遇到了一些麻烦。
根据Apple文档:

Create an observer for the key path and call the observe(_:options:changeHandler) method. For more information on key paths, see Keys and Key Paths.

class MyObserver: NSObject {
    @objc var objectToObserve: MyObjectToObserve
    var observation: NSKeyValueObservation?

    init(object: MyObjectToObserve) {
        objectToObserve = object
        super.init()

        observation = observe(\.objectToObserve.myDate) { object, change in
            print("Observed a change to \(object.objectToObserve).myDate, updated to: \(object.objectToObserve.myDate)")
        }
    }
}

let observed = MyObjectToObserve()
let observer = MyObserver(object: observed)

observed.updateDate()

我正在像这样初始化我的观察:

self.observation = self.webView!.observe(\.webView.isLoading, changeHandler: { (webView, observedChange) in
    //code
})

但出现此错误:

Answer 1

事实证明，语法需要使用对象Type而不是对象实例名称:

self.observation = self.webView!.observe(\WKWebView.isLoading, changeHandler: { (webView, observedChange) in
    //code
})

误读了文档\_(ツ)_/