Fehler: Wert vom Typ 'AppDelegate?' hat kein Mitglied ‚Gegenwart‘

Question

ich einen Fehler von

Value of type 'AppDelegate?' has no member 'present'

als ich versuchte, meine Benutzer bin immer in selbst angemeldet zu halten, wenn der App verlassen wurde.

Hier sind meine View-Controller, eine Idee, wie ich meine Benutzer angemeldet bleiben? Und warum bekomme ich diesen Fehler?

Ich benutze Firebase in meinem Code als meine Datenbank.

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:. 
    } 


} 

Jedwedes Hilfe würde geschätzt.

Answer 1

App-Delegat ist nicht vom Typ ViewController, daher gibt es keine aktuelle Methode, um Ansichten anzuzeigen. Stattdessen können Sie eine Ansicht mit dem folgenden Fenster anzeigen:

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) 
    }