无法将 tabBarController.viewController 转换为 UINavigationController

Question

我在我的故事板中添加了一个 UITabBarController，当我在我的 Appdelegate 中加载 managedContext 时，我想将它传递给我的初始 ViewController。但我不能将 viewControllers 转换为 UINavigationControllers，因此 managedContext 不会加载。

这是我的代码：

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

        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let controller = storyboard.instantiateViewController(withIdentifier: "TabBarVC")
        self.window?.rootViewController = controller



        guard let tabBarController = window?.rootViewController as? UITabBarController else {
            print("1")
            return true
        }
        guard let navController = tabBarController.viewControllers![0] as? UINavigationController else {
            print("2")
            return true
        }
        guard let viewController = navController.topViewController as? ViewController else {

               print("3")

                return true

        }

//  Version that works for UINavigationController
//        guard let navController = window?.rootViewController as? UINavigationController,
//            let viewController = navController.topViewController as? ViewController else {
//                return true
//        }


        viewController.managedContext = coreDataStack.managedContext
        // Override point for customization after application launch.
        return true
    }

当我简单地使用 UINavigationController 时，代码可以正常工作。我做错了什么？

编辑： 我绕过了导航控制器，将序列直接放到了 ViewController 中。现在可以了！

Answer 1

很好，工作

if let tabbarcontroller = segue.destination as? UITabBarController
{
    let navigationController = tabbarcontroller.viewControllers![0] as! UINavigationController
    let controller = navigationController.topViewController as! HomeController
    controller.account = sender as? Account
}