swift 3 WKWebView 委托 WKNavigationDelegate 模糊方法答案

【问题标题】：swift 3 WKWebView delegate WKNavigationDelegate Ambiguous methodswift 3 WKWebView 委托 WKNavigationDelegate 模糊方法
【发布时间】：2016-09-23 10:19:56
【问题描述】：

我创建了一个名为JSBridge的类，这个类实现了WKNavigationDelegate，我在协议方法中做了一些自定义的东西，然后调用另一个UIViewController的默认WKNavigationDelegate，例如WebViewController aka webViewDelegate，所以我必须这样做

func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
    guard let webViewDelegate = webViewDelegate , self.webView == webView else {
        decisionHandler(.allow)
        return
    }

    //do something here then call `WebViewController`'s implementation
    if webViewDelegate.responds(to: #selector(webViewDelegate.webView(_:decidePolicyFor:decisionHandler:))) {
            webViewDelegate.webView!(webView, decidePolicyFor: navigationAction, decisionHandler: decisionHandler)
        } else {
            decisionHandler(.allow)
        }
}

func webView(_ webView: WKWebView, decidePolicyFor navigationResponse: WKNavigationResponse, decisionHandler: @escaping (WKNavigationResponsePolicy) -> Void) {
    guard let webViewDelegate = webViewDelegate , self.webView == webView else {
        decisionHandler(.allow)
        return
    }

    //do something here then 
    if webViewDelegate.responds(to: #selector(webViewDelegate.webView(_:decidePolicyFor:decisionHandler:))) {
        webViewDelegate.webView!(webView, decidePolicyFor: navigationResponse, decisionHandler: decisionHandler)
    } else {
        decisionHandler(.allow)
    }
}

我的问题在 xcode8(swift3) 中，编译器给了我错误： Ambiguous use of 'webView(_:decidePolicyFor:decisionHandler:)'，它们与编译器同名

func webView(_ webView: WKWebView, decidePolicyFor navigationResponse: WKNavigationResponse, decisionHandler: @escaping (WKNavigationResponsePolicy) -> Void)
func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void)

【问题讨论】：

标签： ios swift3 wkwebview

【解决方案1】：

您可以使用as从一些模棱两可的方法中选择一种：

func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
    guard let webViewDelegate = webViewDelegate , self.webView == webView else {
        decisionHandler(.allow)
        return
    }

    typealias WKNavigationActionMethodType = (WKWebView,WKNavigationAction,@escaping(WKNavigationActionPolicy)->Void) -> Void
    if webViewDelegate.responds(to: #selector(webView(_:decidePolicyFor:decisionHandler:) as WKNavigationActionMethodType)) {
        webViewDelegate.webView!(webView, decidePolicyFor: navigationAction, decisionHandler: decisionHandler)
    } else {
        decisionHandler(.allow)
    }
}

处理这种情况的另一种方法是“避免使用responds(to:) 并使用可选链接”：

func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
    guard let webViewDelegate = webViewDelegate , self.webView == webView else {
        decisionHandler(.allow)
        return
    }

    if webViewDelegate.webView?(webView, decidePolicyFor: navigationAction, decisionHandler: decisionHandler) == nil {
        decisionHandler(.allow)
    }
}

委托方法的返回类型是Void，所以它的可选链结果是Void?类型。在您的情况下，仅当实例中未实现可选方法时，它才会变为 nil 。因此，将结果与nil 进行比较是在检查可选方法是否已实现（并实际调用）。

【讨论】：

好方法！