Flutter iOS集成Firebase推送报错：需实现指定FCM token方法

错误提示明确指出你的AppDelegate对象没有响应-messaging:didReceiveRegistrationToken:方法，这是因为你仅声明了遵循MessagingDelegate协议，但没有实现该协议要求的核心方法——FCM需要通过这个方法向App传递设备的推送令牌，完成令牌的获取和更新逻辑。

只需在AppDelegate类中添加以下方法即可解决该问题：

// MARK: - MessagingDelegate
func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String?) {
    guard let token = fcmToken else { return }
    // 可在此将令牌发送到后端服务器，或做其他自定义处理
    print("FCM注册令牌: \(token)")
}

修改后的完整AppDelegate代码如下：

import UIKit
import Flutter
import UserNotifications
import Firebase

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate, MessagingDelegate {
    
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    
        FirebaseApp.configure()
        Messaging.messaging().delegate = self

        GeneratedPluginRegistrant.register(with: self)

        if #available(iOS 10.0, *) {
            UNUserNotificationCenter.current().delegate = self
            let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound]
            UNUserNotificationCenter.current().requestAuthorization(
                    options: authOptions,
                    completionHandler: {_, _ in })
        } else {
            let settings: UIUserNotificationSettings =
            UIUserNotificationSettings(types: [.alert, .badge, .sound], categories: nil)
            application.registerUserNotificationSettings(settings)
        }
        application.registerForRemoteNotifications()

        return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
    
    // MARK: - MessagingDelegate
    func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String?) {
        guard let token = fcmToken else { return }
        print("FCM注册令牌: \(token)")
        // 可选：将令牌同步到你的后端服务
    }
}

添加该方法后，FCM就能正常传递推送令牌，错误会消失；同时你可以在方法内处理令牌的保存或更新逻辑，确保后端能获取到最新的设备令牌用于推送。

内容的提问来源于stack exchange，提问作者Harjinder Bains