ios - swift 3 WKWebView 委托(delegate) WKNavigationDelegate 模糊方法
<p><p>我创建了一个名为<code>JSBridge</code>的类，这个类实现了<code>WKNavigationDelegate</code>，我在protocol方法中做了一些自定义的东西，然后调用另一个<code>UIViewController</code>的默认<code>WKNavigationDelegate</code>，例如<code>WebViewController</code>又名<code>webViewDelegate</code>，所以我必须这样做</p>
<pre><code>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)
}
}
</code></pre>
<p>我的问题出在 xcode8(swift3) 中，编译器给了我错误:
<code>'webView(_:decidePolicyFor:decisionHandler:)'的歧义使用</code>，它们与编译器同名</p>
<pre><code>func webView(_ webView: WKWebView, decidePolicyFor navigationResponse: WKNavigationResponse, decisionHandler: @escaping (WKNavigationResponsePolicy) -> Void)
func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void)
</code></pre></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>您可以使用 <code>as</code> 从一些模棱两可的方法中选择一种:</p>
<pre><code>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)
}
}
</code></pre>
<hr/>
<p>另一种处理这种情况的方法是“避免使用 <code>responds(to:)</code> 并使用可选链接”:</p>
<pre><code>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)
}
}
</code></pre>
<p>委托(delegate)方法的返回类型是<code>Void</code>，所以它的Optional链结结果是<code>Void?</code>类型。在您的情况下，只有在实例中未实现可选方法时，它才会变为 <code>nil</code> 。因此，将结果与 <code>nil</code> 进行比较是在检查可选方法是否已实现(并实际调用)。</p></p>
<p style="font-size: 20px;">关于ios - swift 3 WKWebView 委托(delegate) WKNavigationDelegate 模糊方法，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/39658358/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/39658358/
</a>
</p>
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