错误：使用未解析的标识符'FIRApp'

我一直收到错误使用未解析的标识符'FIRApp' . 我删除了我的派生数据文件夹，更新了pod，并多次重新安装了pod . 我目前正在使用xcode 8.2.1 . 我的pod版本是使用Firebase（3.14.0）使用FirebaseAnalytics（3.7.0）使用FirebaseCoreID（3.5.1）使用FirebaseInstanceID（1.0.9）使用FirebaseMessaging（1.2.2）使用GoogleToolboxForMac（2.1.1）使用Protobuf（3.2.0） .0） . 我正在使用最新版本的cocoapods . 谢谢你的帮忙 .

import UIKit
    import UserNotifications
    import Firebase
    import FirebaseInstanceID
    import FirebaseMessaging

    @UIApplicationMain
    class AppDelegate: UIResponder, UIApplicationDelegate {

        var window: UIWindow?
        let gcmMessageIDKey = "gcm.message_id"

        func application(_ application: UIApplication,
                         didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

            // Register for remote notifications. This shows a permission dialog on first run, to
            // show the dialog at a more appropriate time move this registration accordingly.
            // [START register_for_notifications]
            if #available(iOS 10.0, *) {
                // For iOS 10 display notification (sent via APNS)
                UNUserNotificationCenter.current().delegate = self

                let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound]
                UNUserNotificationCenter.current().requestAuthorization(
                    options: authOptions,
                    completionHandler: {_, _ in })

                // For iOS 10 data message (sent via FCM)
                FIRMessaging.messaging().remoteMessageDelegate = self

            } else {
                let settings: UIUserNotificationSettings =
                    UIUserNotificationSettings(types: [.alert, .badge, .sound], categories: nil)
                application.registerUserNotificationSettings(settings)
            }

            application.registerForRemoteNotifications()

            // [END register_for_notifications]
            FIRApp.configure()

            // [START add_token_refresh_observer]
            // Add observer for InstanceID token refresh callback.
            NotificationCenter.default.addObserver(self,
                                                   selector: #selector(self.tokenRefreshNotification),
                                                   name: .firInstanceIDTokenRefresh,
                                                   object: nil)
            // [END add_token_refresh_observer]
            return true
        }