如何在 Xcode 8 中使用 Swift 3 创建 managedObjectContext？
How to create managedObjectContext using Swift 3 in Xcode 8?
面临问题“类型 'AppDelegate' 的值在新 Xcode 8 中没有成员 'managedObjectContext'（使用 Swift 3，iOS 10）时尝试在视图控制器中创建新上下文
let context = (UIApplication.shared().delegate as! AppDelegate).managedObjectContext
在 Xcode 8 中，AppDelegate.swift 文件中没有 managedObjectContext 的代码。 AppDelegate.swift 中的核心数据堆栈代码仅提供： lazy var persistentContainer: NSPersistentContainer 属性 和 func saveContext () 。没有 managedObjectContext 属性.
如何在 Xcode 8) 中使用 Swift 3 创建 managedObjectContext 或者可能不需要使用 Swift 3 来创建它？
NSPersistentContainer 有一个 viewContext 属性 是 NSManagedObjectContext 类型。
附带说明一下，如果您在 Xcode 8 中创建主从应用程序，Apple 的示例代码会将 managedObjectContext 属性 放入 MasterViewController.swift 文件中，并且通过在 AppDelegate 中使用 viewContext 属性 来设置它。
在 Swift3 中，您可以通过 viewContext 访问 managedObjectContext as
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
如果在创建项目时启用了核心数据，则此选项可用。但是，对于您想要包含核心数据的现有项目，请执行添加核心数据的正常过程并添加以下代码，这将使您获得
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
}()
您将需要导入 CoreData。
注意：对于Swift3，ManagedObject子类是自动生成的。
查看来自 WWDC 2016
的更多信息
James Amo 的解决方案为您提供了 iOS 10.0 的大部分方法，但未解决 iOS 9.0 及以下版本，它们无法访问该方法，并且需要手动构建 NSManagedObjectModel。这是对我有用的解决方案：
var context: NSManagedObjectContext?
if #available(iOS 10.0, *) {
context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
} else {
// iOS 9.0 and below - however you were previously handling it
guard let modelURL = Bundle.main.url(forResource: "Model", withExtension:"momd") else {
fatalError("Error loading model from bundle")
}
guard let mom = NSManagedObjectModel(contentsOf: modelURL) else {
fatalError("Error initializing mom from: \(modelURL)")
}
let psc = NSPersistentStoreCoordinator(managedObjectModel: mom)
context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
let docURL = urls[urls.endIndex-1]
let storeURL = docURL.appendingPathComponent("Model.sqlite")
do {
try psc.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: storeURL, options: nil)
} catch {
fatalError("Error migrating store: \(error)")
}
}
很明显，对 10.0 的更改使 CoreData 变得更加简单，但不幸的是，现有开发人员要进行跳跃是如此痛苦...
要实现上述内容，只需确保将 persistentContainer 放入 AppDelegate.swift 中，定义在 James Amo 的答案中。
将所有核心数据堆栈代码移动到一个文件中，并添加了 iOS 10 和以下 iOS10。下面是我的尝试（不确定是否完全符合标准）
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()
}
}
}
}
首先，获取AppDelegate对象：-
let appDelegateObject = UIApplication.shared.delegate as! AppDelegate
现在，我们可以获得托管对象：
let managedObject = appDelegateObject.persistentContainer.viewContext
面临问题“类型 'AppDelegate' 的值在新 Xcode 8 中没有成员 'managedObjectContext'（使用 Swift 3，iOS 10）时尝试在视图控制器中创建新上下文
let context = (UIApplication.shared().delegate as! AppDelegate).managedObjectContext
在 Xcode 8 中，AppDelegate.swift 文件中没有 managedObjectContext 的代码。 AppDelegate.swift 中的核心数据堆栈代码仅提供： lazy var persistentContainer: NSPersistentContainer 属性 和 func saveContext () 。没有 managedObjectContext 属性.
如何在 Xcode 8) 中使用 Swift 3 创建 managedObjectContext 或者可能不需要使用 Swift 3 来创建它？
NSPersistentContainer 有一个 viewContext 属性 是 NSManagedObjectContext 类型。
附带说明一下，如果您在 Xcode 8 中创建主从应用程序，Apple 的示例代码会将 managedObjectContext 属性 放入 MasterViewController.swift 文件中，并且通过在 AppDelegate 中使用 viewContext 属性 来设置它。
在 Swift3 中，您可以通过 viewContext 访问 managedObjectContext as
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
如果在创建项目时启用了核心数据，则此选项可用。但是，对于您想要包含核心数据的现有项目，请执行添加核心数据的正常过程并添加以下代码，这将使您获得
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
}()
您将需要导入 CoreData。
注意：对于Swift3，ManagedObject子类是自动生成的。 查看来自 WWDC 2016
的更多信息James Amo 的解决方案为您提供了 iOS 10.0 的大部分方法，但未解决 iOS 9.0 及以下版本，它们无法访问该方法，并且需要手动构建 NSManagedObjectModel。这是对我有用的解决方案：
var context: NSManagedObjectContext?
if #available(iOS 10.0, *) {
context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
} else {
// iOS 9.0 and below - however you were previously handling it
guard let modelURL = Bundle.main.url(forResource: "Model", withExtension:"momd") else {
fatalError("Error loading model from bundle")
}
guard let mom = NSManagedObjectModel(contentsOf: modelURL) else {
fatalError("Error initializing mom from: \(modelURL)")
}
let psc = NSPersistentStoreCoordinator(managedObjectModel: mom)
context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
let docURL = urls[urls.endIndex-1]
let storeURL = docURL.appendingPathComponent("Model.sqlite")
do {
try psc.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: storeURL, options: nil)
} catch {
fatalError("Error migrating store: \(error)")
}
}
很明显，对 10.0 的更改使 CoreData 变得更加简单，但不幸的是，现有开发人员要进行跳跃是如此痛苦...
要实现上述内容，只需确保将 persistentContainer 放入 AppDelegate.swift 中，定义在 James Amo 的答案中。
将所有核心数据堆栈代码移动到一个文件中，并添加了 iOS 10 和以下 iOS10。下面是我的尝试（不确定是否完全符合标准）
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()
}
}
}
}
首先，获取AppDelegate对象：-
let appDelegateObject = UIApplication.shared.delegate as! AppDelegate
现在，我们可以获得托管对象：
let managedObject = appDelegateObject.persistentContainer.viewContext