Core Data三表中两表修改未保存，疑与迁移操作相关

使用Core Data存储数据，通过DB Browser for SQLite查看模拟器数据库。执行数据创建流程后，数据库中所有条目和关联正常显示，但重启应用后，FoodItem条目保留，ComposedFoodItem、Ingredient条目及关联关系全部消失。

核心数据创建函数 #

/**
 Creates a new ComposedFoodItem from the ComposedFoodItemViewModel.
 Creates the related FoodItem and the Ingredients.
 Creates all relationships.
 
 - Parameter composedFoodItemVM: The source view model.
 
 - Returns: A Core Data ComposedFoodItem; nil if there are no Ingredients.
 */
static func create(from composedFoodItemVM: ComposedFoodItemViewModel, generateTypicalAmounts: Bool) -> ComposedFoodItem? {
    debugPrint(AppDelegate.persistentContainer.persistentStoreDescriptions) // The location of the .sqlite file
    let moc = AppDelegate.viewContext
    
    // Create new ComposedFoodItem (1)
    let cdComposedFoodItem = ComposedFoodItem(context: moc)
    
    // No existing composed food item, therefore create a new UUID
    cdComposedFoodItem.id = UUID()
    
    // Fill data
    cdComposedFoodItem.amount = Int64(composedFoodItemVM.amount)
    cdComposedFoodItem.numberOfPortions = Int16(composedFoodItemVM.numberOfPortions)
    
    // Create the related FoodItem (2)
    let cdFoodItem = FoodItem.create(from: composedFoodItemVM, generateTypicalAmounts: generateTypicalAmounts)
    
    // Relate both (3)
    cdComposedFoodItem.foodItem = cdFoodItem
    
    // Add cdComposedFoodItem to composedFoodItemVM
    composedFoodItemVM.cdComposedFoodItem = cdComposedFoodItem
    
    // Save before adding Ingredients, otherwise this could lead to an NSInvalidArgumentException (4)
    try? moc.save()
    
    // Add new ingredients (5)
    if let cdIngredients = Ingredient.create(from: composedFoodItemVM) {
        cdComposedFoodItem.addToIngredients(NSSet(array: cdIngredients))
        
        // Save new composed food item
        try? moc.save()
        
        // Return the ComposedFoodItem
        return cdComposedFoodItem
    } else {
        // There are no ingredients, therefore we delete it again and return nil
        moc.delete(cdComposedFoodItem)
        try? moc.save()
        return nil
    }
}

执行流程 #

• 1. 在ComposedFoodItem表创建新条目
• 2. 在FoodItem表创建新条目
• 3. 建立两个条目关联
• 4. 保存修改（此时数据库可见两个新条目及正确关联）
• 5. 在Ingredient表创建1~n个新条目并关联到步骤1的条目

自定义迁移策略背景 #

近期完成了从数据模型版本1（"EasyFPU"）到版本2（"EasyFPU 2"）的Core Data迁移，针对ComposedFoodItem和Ingredient表设置了自定义迁移策略，逻辑一致：

/**
 No Ingredient is created in the destination model, i.e., there will be no Ingredients
 */
override func createDestinationInstances(forSource sourceIngredient: NSManagedObject, in mapping: NSEntityMapping, manager: NSMigrationManager) throws {
    // Do nothing on purpose
    debugPrint("Not migrating Ingredient with ID: \((sourceIngredient as? Ingredient)?.id.uuidString ?? "unknown")")
}

怀疑迁移策略在重启时被触发，但断点未捕获到debugPrint输出，迁移本应已完成。

AppDelegate中Core Data容器配置 #

lazy var persistentContainer: NSPersistentCloudKitContainer = {
    let container = NSPersistentCloudKitContainer(name: "EasyFPU")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        if let error = error as NSError? {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    })
    return container
}()

曾尝试修改容器名从"EasyFPU"到"EasyFPU 2"，但确认容器名称与模型版本无关。

请问有哪些可能的解决思路？

内容的提问来源于stack exchange，提问作者Ulrich