ios - 启动 NSManagedObjectContext 会产生 fatal error ？

Question

我正在处理我的应用程序的最后一段，这似乎是我遇到问题的最后一部分。无论如何，为此祈祷。

我已将 CoreData 全部设置好并准备好在表格中显示(希望我不能在表格中真正查看它以验证)。

我现在遇到的问题是，当加载实现 CoreData 的 View 时，当它启动我的 NSManagedObjectContext 时会发生 fatal error 。请注意，除了 TableViewController 之外，我还使用两个单独的 ViewController 来获取数据，因此我在我的应用程序中总共声明了 3 个 NSManagedContextObjects - 我不确定这是否是问题所在。导致它的行在我的 viewDidLoad 函数中。请参阅下面的代码。

override func viewDidLoad() {
        super.viewDidLoad()

        managedObjectContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    }

我不完全确定如何解决这个问题，因为我一直在遵循整个过程的教程。

编辑:我将添加所有受 CoreData 影响的代码，这样可能有助于解决问题。

这是我的核心数据模型的截图

应用委托(delegate)

import UIKit
import CoreData

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?


func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.
    return true
}

func applicationWillResignActive(_ application: UIApplication) {
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and invalidate graphics rendering callbacks. Games should use this method to pause the game.
}

func applicationDidEnterBackground(_ application: UIApplication) {
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

func applicationWillEnterForeground(_ application: UIApplication) {
    // Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.
}

func applicationDidBecomeActive(_ application: UIApplication) {
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

func applicationWillTerminate(_ application: UIApplication) {
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
    // Saves changes in the application's managed object context before the application terminates.
    //self.saveContext()
}

// 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: "RSDB_1_0_COREDATA")
    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)")
        }
    }
}

第一个 View Controller

let newInfo = GeneralInfo(context:managedObjectContext1)
        newInfo.courseNumber = studCourse
        newInfo.scenarioNumber = studScen

        do {
            try self.managedObjectContext1.save()
        }catch {
            print("Could not save data \(error.localizedDescription)")
        }


        performSegue(withIdentifier: "segue3", sender: self)

不同的 View Controller

 let newEvaluation = GeneralEvaluation(context:managedObjectContext)
        newEvaluation.idScore = String(ID)
        newEvaluation.washScore = String(WASH)
        newEvaluation.totalScore = String(total)

        do {
            try self.managedObjectContext.save()
        }catch {
            print("Could not save data \(error.localizedDescription)")
        }

        performSegue(withIdentifier: "segue4", sender: self)

表格 View Controller

let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! TheTableViewCell

   let info = courseInfo[indexPath.row]
   let score = scores[indexPath.row]

    cell.CLASS.text = info.courseNumber
    cell.SCENARIO.text = info.scenarioNumber

    cell.WASH.text = score.washScore
    cell.ID.text = score.idScore
    cell.TOTAL.text = score.totalScore

Answer 1

查看错误消息的文本和堆栈跟踪会很有帮助。

您可以从分解调用链开始，缩小崩溃的范围。

let appDelegate = (UIApplication.shared.delegate as! AppDelegate)
let container = appDelegate.persistentContainer
managedObjectContext = container.viewContext

你的堆栈(持久容器/持久存储协调器/托管对象模型/托管对象上下文在你加载 View Controller 之前实例化了吗？看起来没有。因为你这么早就崩溃了，我会走出困境并猜测某处存在拼写错误或名称不匹配(文件名与定义代码中的内容不匹配)。或者您的 MOM 未作为资源包含在您的包中？