如何在iOS上显示使用firebase-cpp-sdk接收到的FCM 'data‘消息？

import Firebase
import FirebaseMessaging

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    FirebaseApp.configure()
    Messaging.messaging().delegate = self
    // 其他初始化代码
    return true
}

extension AppDelegate: MessagingDelegate {
    func messaging(_ messaging: Messaging, didReceive remoteMessage: MessagingRemoteMessage) {
        if let messageData = remoteMessage.appData["data"] as? [String: Any] {
            // 在这里处理接收到的FCM 'data'消息
            // 可以使用UIAlertController或其他方式将消息内容显示在应用程序界面上
        }
    }
}

func showAlert(withMessage message: String) {
    let alertController = UIAlertController(title: "FCM Message", message: message, preferredStyle: .alert)
    let okAction = UIAlertAction(title: "OK", style: .default, handler: nil)
    alertController.addAction(okAction)
    self.present(alertController, animated: true, completion: nil)
}