import CoreData struct PersistenceController { static let shared = PersistenceController() static var preview: PersistenceController = { let result = PersistenceController(inMemory: true) let viewContext = result.container.viewContext do { try viewContext.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)") } return result }() let container: NSPersistentContainer init(inMemory: Bool = false) { container = NSPersistentContainer(name: "Yattee") if inMemory { container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null") } container.viewContext.automaticallyMergesChangesFromParent = true container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy container.loadPersistentStores { _, 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)") } } } }