我正在使用SwiftUI构建一个简单的Web应用程序，它只需将我的网站加载到Web视图中。从我的网站上，它必须显示JavaScript confirm，以便用户能够从应用程序中注销，而我的runJavaScriptConfirmPanelWithMessage内部的函数在Javascript确认被触发时会导致应用程序崩溃。
下面是我的Web应用程序的完整代码。

import SwiftUI
import WebKit

struct Webview : UIViewRepresentable {
    let request: URLRequest
    var webview: WKWebView?

    init(web: WKWebView?, req: URLRequest) {
        self.webview = WKWebView()
        self.request = req
    }

    class Coordinator: NSObject, WKUIDelegate {
        var parent: Webview

        init(_ parent: Webview) {
            self.parent = parent
        }

        // Delegate methods go here

        func webView(_ webView: WKWebView,
        runJavaScriptAlertPanelWithMessage message: String,
             initiatedByFrame frame: WKFrameInfo,
             completionHandler: @escaping () -> Void) {

            // alert functionality goes here
            let alertController = UIAlertController(title: nil, message: message, preferredStyle: .alert)

            alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))

            alertController.present(alertController, animated: true)

            completionHandler()

        }

        func webView(_ webView: WKWebView,
        runJavaScriptConfirmPanelWithMessage message: String,
             initiatedByFrame frame: WKFrameInfo,
             completionHandler: @escaping (Bool) -> Void) {

            // confirm functionality goes here. THIS CRASHES THE APP
            let alertController = UIAlertController(title: nil, message: message, preferredStyle: .alert)

            alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
                completionHandler(true)
            }))

            alertController.addAction(UIAlertAction(title: "Cancel", style: .default, handler: { (action) in
                completionHandler(false)
            }))

            alertController.present(alertController, animated: true, completion: nil)
        }

        func webView(_ webView: WKWebView,
        runJavaScriptTextInputPanelWithPrompt prompt: String,
                  defaultText: String?,
             initiatedByFrame frame: WKFrameInfo,
             completionHandler: @escaping (String?) -> Void) {

            // prompt functionality goes here

        }
    }

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    func makeUIView(context: Context) -> WKWebView  {
        return webview!
    }

    func updateUIView(_ uiView: WKWebView, context: Context) {
        uiView.uiDelegate = context.coordinator
        uiView.load(request)
    }

    func goBack(){
        webview?.goBack()
    }

    func goForward(){
        webview?.goForward()
    }

    func reload(){
        webview?.reload()
    }
}

struct ContentView: View {

    let webview = Webview(web: nil, req: URLRequest(url: URL(string: "https://google.com")!))

    var body: some View {
        VStack {
            webview
            HStack() {
                Button(action: {
                    self.webview.goBack()
                }){
                    Image(systemName: "chevron.left")
                }.padding(32)

                Button(action: {
                    self.webview.reload()
                }){
                    Image(systemName: "arrow.clockwise")
                }.padding(32)

                Button(action: {
                    self.webview.goForward()
                }){
                    Image(systemName: "chevron.right")
                }.padding(32)
            }.frame(height: 40)
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

字符串
我不知道我在runJavaScriptConfirmPanelWithMessage的这一节中做错了什么，使应用程序崩溃。
这就是我遇到麻烦的地方。

func webView(_ webView: WKWebView,
        runJavaScriptConfirmPanelWithMessage message: String,
             initiatedByFrame frame: WKFrameInfo,
             completionHandler: @escaping (Bool) -> Void) {

            // confirm functionality goes here. THIS CRASHES THE APP
            let alertController = UIAlertController(title: nil, message: message, preferredStyle: .alert)

            alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
                completionHandler(true)
            }))

            alertController.addAction(UIAlertAction(title: "Cancel", style: .default, handler: { (action) in
                completionHandler(false)
            }))

            alertController.present(alertController, animated: true, completion: nil)
        }

型
谁能告诉我我做错了什么？