¿Cómo crear managedObjectContext usando Swift 3 en Xcode 8?

Enfrentando el problema “Valor del tipo ‘AppDelegate’ no tiene miembro ‘managedObjectContext’ en el nuevo Xcode 8 (usando Swift 3, iOS 10) cuando se intenta crear un contexto nuevo en View Controller

let context = (UIApplication.shared().delegate as! AppDelegate).managedObjectContext 

En Xcode 8 no hay código para managedObjectContext dentro del archivo AppDelegate.swift. El código de stack de Core Data dentro de AppDelegate.swift solo se presenta con: lazy var persistentContainer: propiedad NSPersistentContainer y func saveContext (). No hay propiedad managedObjectContext.

¿Cómo crear managedObjectContext usando Swift 3 en Xcode 8) o tal vez no hay necesidad de hacerlo usando Swift 3?

En Swift3, puede acceder al managedObjectContext a través de viewContext como

 let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext 

Esta opción está disponible si se habilitaron los datos principales al crear el proyecto. Sin embargo, para el proyecto existente que desee incluir datos básicos, realice el proceso normal de agregar los datos principales y agregue el siguiente código que le permitirá obtener el

 lazy var persistentContainer: NSPersistentContainer = { let container = NSPersistentContainer(name: "you_model_file_name") container.loadPersistentStores(completionHandler: { (storeDescription, error) in if let error = error { fatalError("Unresolved error \(error), \(error.userInfo)") } }) return container }() 

Necesitarás importar el CoreData.

Nota: para Swift3, la Subclase ManagedObject se genera automáticamente. Ver más de WWDC 2016

Se movió todo el código de stack de datos central a un solo archivo y se agregó iOS 10 y debajo iOS10. a continuación es mi bash (no estoy seguro de que esté completamente a la altura de la marca)

 import Foundation import CoreData class CoreDataManager { // MARK: - Core Data stack static let sharedInstance = CoreDataManager() private lazy var applicationDocumentsDirectory: URL = { // The directory the application uses to store the Core Data store file. This code uses a directory named in the application's documents Application Support directory. let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask) return urls[urls.count-1] }() private lazy var managedObjectModel: NSManagedObjectModel = { // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model. let modelURL = Bundle.main.url(forResource: "CoreDataSwift", withExtension: "momd")! return NSManagedObjectModel(contentsOf: modelURL)! }() private lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = { // The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added 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. // Create the coordinator and store let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel) let url = self.applicationDocumentsDirectory.appendingPathComponent("CoreDataSwift.sqlite") var failureReason = "There was an error creating or loading the application's saved data." do { // Configure automatic migration. let options = [ NSMigratePersistentStoresAutomaticallyOption : true, NSInferMappingModelAutomaticallyOption : true ] try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: options) } catch { // Report any error we got. var dict = [String: AnyObject]() dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" as AnyObject? dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject? dict[NSUnderlyingErrorKey] = error as NSError let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict) // Replace this with code to handle the error appropriately. // abort() 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. NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)") abort() } return coordinator }() lazy var managedObjectContext: NSManagedObjectContext = { var managedObjectContext: NSManagedObjectContext? if #available(iOS 10.0, *){ managedObjectContext = self.persistentContainer.viewContext } else{ // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail. let coordinator = self.persistentStoreCoordinator managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType) managedObjectContext?.persistentStoreCoordinator = coordinator } return managedObjectContext! }() // iOS-10 @available(iOS 10.0, *) 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: "CoreDataSwift") 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)") } }) print("\(self.applicationDocumentsDirectory)") return container }() // MARK: - Core Data Saving support func saveContext () { if managedObjectContext.hasChanges { do { try managedObjectContext.save() } catch { // Replace this implementation with code to handle the error appropriately. // abort() 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 NSLog("Unresolved error \(nserror), \(nserror.userInfo)") abort() } } } }