entityForName: nil 不是用于搜索实体名称的合法 NSPersistentStoreCoordinator

Question

我设置了一个 DatabaseApplicationService

• 获取以编程方式定义的 NSManagedObjectModel
• 基于该模型创建一个 NSPersistentCloudKitContainer，有“Local”和“Cloud”两种配置。

看起来一切都很好。

    lazy var persistentContainer: NSPersistentCloudKitContainer = {

        // Ensure that we have the required path.
        pathHandler.ensurePersistentStorePath()

        #if DEBUG
        // get the store description
        guard let description = container.persistentStoreDescriptions.first
            else {
                fatalError("Could not retrieve a persistent store description.")
            }

        // initialize the CloudKit schema
        try? container.initializeCloudKitSchema(options: NSPersistentCloudKitContainerSchemaInitializationOptions.dryRun)

        #endif

        let local = NSPersistentStoreDescription(url: pathHandler.persistentLocalStoreURL)
        local.configuration = "Local"

        let cloud = NSPersistentStoreDescription(url: pathHandler.persistentCloudStoreURL)
        cloud.configuration = "Cloud"

        cloud.cloudKitContainerOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: "iCloud.com.innoreq.HappyFreelancer")
        container.persistentStoreDescriptions = [ local, cloud ]

        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
    }()

在

SceneDelegate

中，环境获得注入的NSManagedObjectContext：

        let contentView = ContentView().environment(\.managedObjectContext, databaseService.context)

在视图的模型中，环境被要求提供上下文：

    @Environment(\.managedObjectContext) var managedObjectContext: NSManagedObjectContext

现在，当从上下文中获取数据时：

let fetchRequest: NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "EWork")

        do {

            return try managedObjectContext.execute(fetchRequest) as! [IsTimedAndTagged]
        } catch {

            fatalError("Failed to fetch EWork")
        }

运行时抛出此错误：

2020-01-23 16:34:05.981483+0100 XY[14121:20859222] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+entityForName: nil is not a legal NSPersistentStoreCoordinator for searching for entity name 'EWork''

检查服务协调器时，它是notnil。对于这种奇怪的效果有什么解释吗？

Answer 1

对于那些使用 Swift5 并且没有 Appdelegate 并尝试创建 NFSRequest 查询的人。

您可能会缺少持久存储，因此创建您自己的自定义存储可能会起作用。因为那是我的问题。

创建您自己的 PersistentContainer 类：

import SwiftUI
import CoreData
@main
struct TestApp: App {
        let context = PersistentCloudKitContainer.persistentContainer.viewContext
        var body: some Scene {
                WindowGroup {
                        ContentView().environment(\.managedObjectContext, context)
                }
        }
}

然后你的自定义类是这样的：

import CoreData
public class PersistentCloudKitContainer {
        // MARK: - Define Constants / Variables
        public static var context: NSManagedObjectContext {
                return persistentContainer.viewContext
        }
        // MARK: - Initializer
        private init() {}
        // MARK: - Core Data stack
        public static var persistentContainer: NSPersistentContainer = {
                let container = NSPersistentContainer(name: "Model")
                container.loadPersistentStores(completionHandler: { (storeDescription, error) in
                        if let error = error as NSError? {
                                fatalError("Unresolved error \(error), \(error.userInfo)")
                        }
                })
                container.viewContext.automaticallyMergesChangesFromParent = true
                container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
                return container
        }()
        // MARK: - Core Data Saving support
        public static func saveContext () {
                let context = persistentContainer.viewContext
                if context.hasChanges {
                        do {
                                try context.save()
                        } catch {
                                let nserror = error as NSError
                                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
                        }
                }
        }
}

希望它能帮助像我这样可能最终会在这里寻找答案的人！

Answer 2

当我尝试在子上下文中创建新的 NSManagedObject 但子上下文没有分配持久存储时，我遇到了同样的错误。

代码产生错误：

let childContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType) // The context doesn't have related persistent store
let newObject = NSEntityDescription.insertNewObject(forEntityName: entityName, into: childContext) // The error occurred when trying to find the entity from a nil persistent store

将持久存储添加到子上下文修复了错误。

@Environment(\.managedObjectContext) var moc
let childContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
childContext.persistentStoreCoordinator = moc.persistentStoreCoordinator // add persistent store to the context

let newObject = NSEntityDescription.insertNewObject(forEntityName: entityName, into: childContext) 

参考：https://blog.csdn.net/weixin_40200876/article/details/87866492

希望有帮助:)