SWIFT 3 WKWebView委托WKNavigationDelegate暧昧方法

Question

我创建了一个名为JSBridge类，这个类实现了WKNavigationDelegate，我做了一些定制的东西，在协议的方法，然后调用另一个UIViewController的默认WKNavigationDelegate，例如WebViewController又名webViewDelegate，使我必须做这样的

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) 
    } 
} 

我的问题是在xcode8（swift3）编译器给我的错误： Ambiguous use of 'webView(_:decidePolicyFor:decisionHandler:)'，它们具有相同的名称编译器

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选择一个从一些模棱两可的方法：

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) 
    } 
} 

---

另一种方式来看待这种情况是“避免使用responds(to:)和使用可选链”：

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为Void，所以其可选链接结果的类型为Void?。在你的情况下，只有在实例中没有实现可选方法时，它才变为nil。因此，将结果与nil进行比较是检查可选方法是否已实现（并且实际调用）。