将 CoreData 集成到我的 ToDo 应用程序时出现黑屏 Swift

Question

我正在通过在线课程学习 Swift，当我的讲师将 CoreData 集成到她现有的代码中时，她创建了一个新的核心数据模型并复制粘贴 App Delegate。但是在她的 DataModel 中，没有 SceneDelegate，而在我的中有。

问题是因为这些差异，我不能做和她一样的事情。因此，我将 SceneDelegate.swift 文件复制到我的 Xcode 项目中，并从 DataModel App Delegate 复制了其他内容。

经过这个解决后，我黑屏了。

我不知道我是否应该添加她和我的应用程序委托，但不同之处在于我在核心数据模型应用程序委托中没有 applicationWillResignActive、applicationDidEnterBackgraound 等，而她有。

存在这些差异时，如何将 CoreData 集成到我的项目中？

谢谢！

这是我的应用委托文件

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?


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


        return true
    }

    func applicationWillResignActive(_ application: UIApplication) {

    }

    func applicationDidEnterBackground(_ application: UIApplication) {

    }

    func applicationWillEnterForeground(_ application: UIApplication) {

    }

    func applicationDidBecomeActive(_ application: UIApplication) {

    }

    func applicationWillTerminate(_ application: UIApplication) {

    }
}

Answer 1

您需要这些代码行：

// MARK: - Core Data stack

lazy var persistentContainer: NSPersistentContainer = {
    /*
     The persistent container for the application. This implementation
     creates and returns a container, having loaded the store for the
     application to it. This property is optional since there are legitimate
     error conditions that could cause the creation of the store to fail.
    */
    let container = NSPersistentContainer(name: "TestCoreData")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        if let error = error as NSError? {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

            /*
             Typical reasons for an error here include:
             * The parent directory does not exist, cannot be created, or disallows writing.
             * The persistent store is not accessible, due to permissions or data protection when the device is locked.
             * The device is out of space.
             * The store could not be migrated to the current model version.
             Check the error message to determine what the actual problem was.
             */
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    })
    return container
}()

// MARK: - Core Data Saving support

func saveContext () {
    let context = persistentContainer.viewContext
    if context.hasChanges {
        do {
            try context.save()
        } catch {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            let nserror = error as NSError
            fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
        }
    }
}

将其放在 applicationWillTerminate 函数之后但在 AppDelegate class 内。

创建 Xcode 项目并选中 'Use Core Data' 复选框时会自动添加代码。您始终可以创建一个新的 Xcode 项目，选中 'Use Core Data' 复选框，然后将代码复制并粘贴到自动创建的 AppDelegate 末尾附近。

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