如何使对话框“您正在使用3G。连接到WiFi"？

import SystemConfiguration

func checkNetworkConnection() {
    let reachability = SCNetworkReachabilityCreateWithName(nil, "www.apple.com")
    var flags = SCNetworkReachabilityFlags()
    SCNetworkReachabilityGetFlags(reachability!, &flags)
    
    if flags.contains(.isWWAN) {
        // 当前网络连接为3G
        showAlertDialog("您正在使用3G。连接到WiFi")
        openWiFiSettings()
    }
}

func showAlertDialog(_ message: String) {
    let alertController = UIAlertController(title: nil, message: message, preferredStyle: .alert)
    alertController.addAction(UIAlertAction(title: "确定", style: .default, handler: nil))
    UIApplication.shared.keyWindow?.rootViewController?.present(alertController, animated: true, completion: nil)
}

func openWiFiSettings() {
    guard let url = URL(string: UIApplication.openSettingsURLString) else { return }
    if UIApplication.shared.canOpenURL(url) {
        UIApplication.shared.open(url, options: [:], completionHandler: nil)
    }
}