Question

我在我的故事板中添加了一个UITabBarController，因为我在Appdelegate中加载了managedContext，我希望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
    }

当我使用UINavigationController时，代码正常工作。我做错了什么？

编辑：我绕过导航控制器并将seque直接放到ViewController上。它现在有效！

Answer 1

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
}

无法将tabBarController.viewController转换为UINavigationController

1 个答案: