SWIFT 3 WKWebView委託WKNavigationDelegate曖昧方法

Question

我創建了一個名爲JSBridge類，這個類實現了WKNavigationDelegate，我做了一些定製的東西，在協議的方法，然後調用另一個UIViewController的默認WKNavigationDelegate，例如WebViewController又名webViewDelegate，使我必須做這樣的

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) 
    } 
} 

我的問題是在xcode8（swift3）編譯器給我的錯誤： Ambiguous use of 'webView(_:decidePolicyFor:decisionHandler:)'，它們具有相同的名稱編譯器

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

Answer 1

您可以使用as選擇一個從一些模棱兩可的方法：

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) 
    } 
} 

---

另一種方式來看待這種情況是「避免使用responds(to:)和使用可選鏈」：

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) 
    } 
} 

委託方法的返回類型爲Void，所以其可選鏈接結果的類型爲Void?。在你的情況下，只有在實例中沒有實現可選方法時，它才變爲nil。因此，將結果與nil進行比較是檢查可選方法是否已實現（並且實際調用）。