使用 SceneDelegate 设置 CoreData - 未知标识符 'window' 错误 - iOS 13 起

Question

我试图使用 Core Data 的官方苹果文档。找到 here. I also ran into a question which was related to my issue, right here on .

我运行遇到一个问题，它一直说 'window' 在 AppDelegate 的上下文中不可用。根据官方文档，这是非常基本的步骤。

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {        
    if let rootVC = window?.rootViewController as? ViewController {
        rootVC.container = persistentContainer
    }        
    return true
}

我该如何克服这个问题？

Answer 1

问题归结为更改，主要是 iOS 13 及更高版本中对多个场景的支持。检查这个 reddit link for the discussion.

解决方案是将一些东西从 AppDelegate 移动到 SceneDelegate。

这里是上面两个重要部分的最终形式类。

----场景代理

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    guard let windowScene = (scene as? UIWindowScene) else { return }
    self.window = UIWindow(windowScene: windowScene)
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    guard let rootVC = storyboard.instantiateViewController(identifier: "ViewController") as? ViewController else {
        print("ViewController not found")
        return
    }
    //set the storage here
    rootVC.container = (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer
    //I dont want a  UI navigation controller.
    //let rootNC = UINavigationController(rootViewController: rootVC)
    //self.window?.rootViewController = rootNC
    //I want to use my basic view controller here. use rootNC to get a UI navigation controller
    self.window?.rootViewController = rootVC
    self.window?.makeKeyAndVisible()

}

--AppDelegate（保持不变）

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.
    //before iOS 13 you would be putting stuff here but not anymore.
    return true
}

最后，您将在 AppDelegate 本身中保留与存储相关的代码。

使用 SceneDelegate 设置 CoreData - 未知标识符 'window' 错误 - iOS 13 起

Setting Up CoreData with SceneDelegate - unknown identifier 'window' error - iOS 13 onwards

core-data

ios13

appdelegate

uiwindow

uiscenedelegate