我正尝试使用Apple的官方文档获取Core Data。找到here。我也遇到了一个与我的问题有关的问题,就在stack。
我遇到一个问题,它一直说在AppDelegate的上下文中'window'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?
问题归结为更改,主要是支持iOS 13及更高版本中的多个场景。检查此reddit link for the discussion。
解决方案是将某些东西从AppDelegate移到SceneDelegate。
这是以上两个类别的基本部分的最终形式。
---- SceneDelegate
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,您将把与存储相关的代码保留在AppDelegate本身中。