swift - Swift，试图创建一个保持登录状态，但是实现的代码不起作用

Question

我是 Swift 的新手，我正在关注一个教程，我正在尝试创建一个函数，用户可以在我尝试实现的应用程序中在 Swift 中重新启动时保持登录状态。

使用如下所示的代码

import UIKit
import Parse

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
//variable for window
var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.

        // Initialize Parse
        // Set applicationId and server based on the values in the Heroku settings.
        Parse.initialize(
            with: ParseClientConfiguration(block: { (configuration: ParseMutableClientConfiguration) -> Void in
                configuration.applicationId = "parsetagram"
                configuration.server = "https://secret-taiga-34447.herokuapp.com/parse"
            })
        )

        if PFUser.current() != nil {
            let main = UIStoryboard(name: "Main", bundle: nil)
            let feedNavigationController = main.instantiateViewController(withIdentifier: "FeedNavigationController")

            window?.rootViewController = feedNavigationController
        }


        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:.
    }

}

特别是这部分：

if PFUser.current() != nil {
            let main = UIStoryboard(name: "Main", bundle: nil)
            let feedNavigationController = main.instantiateViewController(withIdentifier: "FeedNavigationController")

            window?.rootViewController = feedNavigationController
        }

它应该允许用户在重新启动后保持登录状态，但是，它不允许。教程的一部分还将导航控制器命名为“FeedNavigationController”，我这样做了，但它仍然没有实现保持登录功能。

在这种情况下会出现什么问题？

标签： swiftswift5