Question

@IBAction func start(sender: UIButton)
{
    var appDel: AppDelegate = (UIApplication.sharedApplication().delegate as    AppDelegate)
    var context: NSManagedObjectContext = appDel.managedObjectContext

    var newUser = NSEntityDescription.insertNewObjectForEntityForName("Users", inManagedObjectContext: context) as NSManagedObject
    newUser.setValue(label!.text, forKey: "score")

    context.save(nil)

    startGame()
    startButton!.enabled = (startButton!.titleLabel!.text == "Start")
}

当我使用NSManagedObjectContext时，它说我需要打开该值，但是当我这样做时，会弹出一个致命的错误，＆＃34;在打开一个可选值＆＃34;时找到nil。我没有将NSManagedObjectContext设置为可选类型。谁能帮我？感谢。

Answer 1

在我看来，您应该遵循最新的Apple Xcode模板并使用可选的：

lazy var managedObjectContext: NSManagedObjectContext? = {
   let coordinator = self.persistentStoreCoordinator
   if coordinator == nil {
       return nil
   }
   var managedObjectContext = NSManagedObjectContext()
   managedObjectContext.persistentStoreCoordinator = coordinator
   return managedObjectContext
}()

和

let context = appDelegate.managedObjectContext!

未解包的可选类型NSManagedObjectContext的值

1 个答案: