錯誤：值類型為“ AppDelegate？” 沒有成員“出席”

Question

我有一個錯誤

“ AppDelegate”類型的值？ 沒有成員“出席”

當我試圖保持我的用戶登錄（即使應用程序退出）時。

這是我的視圖控制器，您知道如何保持用戶登錄狀態嗎？ 為什么我會收到此錯誤？

我在代碼中使用Firebase作為數據庫。

LoginViewController.swift

import UIKit
import Firebase

class LoginViewController: UIViewController, UITextFieldDelegate {

    @IBOutlet weak var emailField: UITextField!
    @IBOutlet weak var pwField: UITextField!




    func createAlert(title:String, message:String) {

        let alert=UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)


        alert.addAction(UIAlertAction(title: "error" , style: UIAlertActionStyle.default, handler: { (action) in alert.dismiss(animated: true, completion: nil)
        }))

        self.present(alert, animated:true, completion: nil)
    }





  /*  @IBAction func emailKeyboardField(_ sender: Any) {

       hideKeyboard()
    }

    func hideKeyboard() {
        emailField.resignFirstResponder()
        pwField.resignFirstResponder()

    }
    */

    override func viewDidLoad() {
        super.viewDidLoad()

        emailField.delegate = self


        // Do any additional setup after loading the view.
    }



    func emailKeyField(_ emailField: UITextField) -> Bool {
        self.view.endEditing(true)


        return true
    }


    @IBAction func loginPressed(_ sender: Any) {

        guard emailField.text != "", pwField.text != "" else {return}

        FIRAuth.auth()?.signIn(withEmail: emailField.text!, password: pwField.text!, completion: { (user, error) in

            if let error = error {
                print(error.localizedDescription)

                self.createAlert(title: "Error", message: "We could not locate your account. Check your email and password.")
            }


            if let user = user {
                let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "usersVC")

                self.present(vc, animated: true, completion: nil)
            }
        })


    }


}

AppDelegate.swift

import UIKit
import Firebase


@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    var window: UIWindow?
    var actIdc = UIActivityIndicatorView(activityIndicatorStyle: .whiteLarge)
    var container: UIView!
    private let auth = FIRAuth.auth()

    class func instance() -> AppDelegate {
        return UIApplication.shared.delegate as! AppDelegate
    }


    func showActivityIndicator() {
        if let window = window {
            container = UIView()
            container.frame = window.frame
            container.center = window.center
            container.backgroundColor = UIColor(white: 0, alpha: 0.8)

            actIdc.frame = CGRect(x: 0, y: 0, width: 40, height: 40)
            actIdc.hidesWhenStopped = true
            actIdc.center = CGPoint(x: container.frame.size.width / 2, y: container.frame.size.height / 2)

            container.addSubview(actIdc)
            window.addSubview(container)

            actIdc.startAnimating()
        }
    }

    func dismissActivityIndicatos() {
        if let _ = window {
            container.removeFromSuperview()
        }
    }

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



                auth?.addStateDidChangeListener { [weak self] (_, user) in

                    if let user = user {
                        let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "usersVC")

                        self.present(vc, animated: true, completion: nil) //error on this line
                        // user is already logged in
                    } else {
                        // user is not logged in
                    }


        }
        FIRApp.configure()
        return true
    }


    func applicationWillResignActive(_ application: UIApplication) {
        // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
        // Use this method to pause ongoing tasks, disable timers, and invalidate graphics rendering callbacks. Games should use this method to pause the game.
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
        // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
        // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
        // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
        // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
    }

    func applicationWillTerminate(_ application: UIApplication) {
        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
    }


}

任何和所有幫助將不勝感激。

Answer 1

應用程序委托不是ViewController類型，因此它沒有當前的方法來顯示視圖。 相反，您可以做的是使用如下窗口顯示視圖：

let storyboard : UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
    let homeC = storyboard.instantiateViewController(withIdentifier: "YOUR_VIEWCONTROLLER_IDENTIFIER_IN_STORYBOARD") as? HomeC
    if homeC != nil {
        homeC!.view.frame = (self.window!.frame)
        self.window!.addSubview(homeC!.view)
        self.window!.bringSubview(toFront: homeC!.view)
    }