ios - 在 UITabBarController 之前呈现登录 View Controller

Question

我想提供一个登录 View Controller ，以便我的用户可以在显示选项卡栏 Controller 之前进行身份验证。在下面显示的代码中，我收到错误“无法将‘LogInViewController’类型的值转换为‘UITabBarController’。列出了 Apple 文档:

When deploying a tab bar interface, you must install this view as the root of your window. Unlike other view controllers, a tab bar interface should never be installed as a child of another view controller.

当我在作为选项卡栏 Controller 一部分的 5 个 View Controller (例如，controller1.coreDataStack = coreDataStack，声明为 AppDelegate 类中的属性)之间传播核心数据时，我感到很困惑，而且我的实现很复杂。我可以获得一些有关如何将用户从登录屏幕转换到选项卡式 View Controller 之一的帮助吗？任何意见将不胜感激。

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

    // Login View Controller
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let loginVC = storyboard.instantiateViewController(withIdentifier: "loginVC") as! LogInViewController
    self.window?.rootViewController = loginVC

    // TabBar Controller
    let tabController = window!.rootViewController as! UITabBarController
    if let tabViewControllers = tabController.viewControllers {
        // First tab (only one so far...)
        let navController = tabViewControllers[0] as! UINavigationController
        let controller1 = navController.viewControllers.first as! FirstViewController
        controller1.coreDataStack = coreDataStack
    }
}

Answer 1

由于尝试强制将 LogInViewController 解包到 UITabBarController，因此出现错误。

对于您的设计流程，在数据库中存储用户的登录状态，在设置window.rootViewController之前对此进行检查，如果用户已登录，则显示 tabController，否则显示LogInViewController。

        let userLogined = GET LOGIN STATUS FROM DATABSE
        if userLogined{
            // Initiate Tabbar Controller object
            let tabController = INITIATE_TABBAR_CONTROLLER
            let tabViewControllers = tabController.viewControllers
            // First tab (only one so far...)
            let navController = tabViewControllers[0] as! UINavigationController
            let controller1 = navController.viewControllers.first as! FirstViewController
            controller1.coreDataStack = coreDataStack
            self.window?.rootViewController = tabController

        }else{
            // Login View Controller
            let storyboard = UIStoryboard(name: "Main", bundle: nil)
            let loginVC = storyboard.instantiateViewController(withIdentifier: "loginVC") as! LogInViewController
            self.window?.rootViewController = loginVC
        }