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我收到一个名为“+ entityForName：nil不是合法的NSManagedObjectContext参数搜索实体名称”Person“的错误。实体的名称是Person，实体名称是设置为字符串的名称。整个过程就是这样一个用户可以添加一个用户名，这可以保存为核心数据。任何方式来解决这个问题？在AppDelegate类也是在代码对于实体名称为零的核心数据的实体
class TableViewUsernameViewController: UIViewController {
@IBOutlet weak var tableView: UITableView!
var people: [NSManagedObject] = []
override func viewDidLoad() {
super.viewDidLoad()
title = "The List"
tableView.register(UITableViewCell.self, forCellReuseIdentifier: "Cell")
// Do any additional setup after loading the view.
}
@IBAction func addName(_ sender: Any) {
let alert = UIAlertController(title: "New Name",
message: "Add a new name",
preferredStyle: .alert)
let saveAction = UIAlertAction(title: "Save", style: .default) {
[unowned self] action in
guard let textField = alert.textFields?.first,
let nameToSave = textField.text else {
return
}
self.save(name: nameToSave)
self.tableView.reloadData()
}
let cancelAction = UIAlertAction(title: "Cancel",
style: .default)
alert.addTextField()
alert.addAction(saveAction)
alert.addAction(cancelAction)
present(alert, animated: true)
}
func save(name: String) {
guard let appDelegate =
UIApplication.shared.delegate as? AppDelegate else {
return
}
// 1
let managedContext =
appDelegate.persistentContainer.viewContext
// 2
let entity =
NSEntityDescription.entity(forEntityName: "Person",
in: managedContext)!
let person = NSManagedObject(entity: entity,
insertInto: managedContext)
// 3
person.setValue(name, forKeyPath: "name")
// 4
do {
try managedContext.save()
people.append(person)
} catch let error as NSError {
print("Could not save. \(error), \(error.userInfo)")
}
}
}
// MARK: - UITableViewDataSource
extension TableViewUsernameViewController: UITableViewDataSource {
func tableView(_ tableView: UITableView,
numberOfRowsInSection section: Int) -> Int {
return people.count
}
func tableView(_ tableView: UITableView,
cellForRowAt indexPath: IndexPath)
-> UITableViewCell {
let person = people[indexPath.row]
let cell =
tableView.dequeueReusableCell(withIdentifier: "Cell",
for: indexPath)
cell.textLabel?.text =
person.value(forKeyPath: "name") as? String
return cell
}
}
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
func application(_ application: UIApplication,
didFinishLaunchingWithOptions launchOptions:
[UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// Override point for customization after application launch.
return true
}
func applicationWillResignActive(_ application: UIApplication) {
// Sent when the application is about to move from active to
inactive state. This can occur for certain types of temporary
interruptions (such as an incoming phone call or SMS message) or
when the user quits the application and it begins the transition to
the background state.
// Use this method to pause ongoing tasks, disable timers, and
invalidate graphics rendering callbacks. Games should use this
method to pause the game.
}
func applicationDidEnterBackground(_ application: UIApplication) {
// Use this method to release shared resources, save user data,
invalidate timers, and store enough application state information to
restore your application to its current state in case it is terminated
later.
// If your application supports background execution, this method
is called instead of applicationWillTerminate: when the user quits.
}
func applicationWillEnterForeground(_ application: UIApplication) {
// Called as part of the transition from the background to the
active state; here you can undo many of the changes made on entering
the background.
}
func applicationDidBecomeActive(_ application: UIApplication) {
// Restart any tasks that were paused (or not yet started) while
the application was inactive. If the application was previously in the
background, optionally refresh the user interface.
}
func applicationWillTerminate(_ application: UIApplication) {
// Called when the application is about to terminate. Save data if
appropriate. See also applicationDidEnterBackground:.
// Saves changes in the application's managed object context before
the application terminates.
self.saveContext()
}
// MARK: - Core Data stack
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: "QuizFinal")
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
}()
// MARK: - Core Data Saving support
func saveContext() {
let context = persistentContainer.viewContext
if context.hasChanges {
do {
try context.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)")
}
}
}
}
//short-cut to access App Delegate
let ad = UIApplication.shared.delegate as! AppDelegate
let context = ad.persistentContainer.viewContext
这行是 –
错误你'managedContext'为零。由于这是从App Delegate中的persistentContainer派生的，请从App Delegate中显示该代码。 – pbasdf
我编辑了我的问题并添加了App Delegate。谢谢 – Jonathon