Swift : Ne peut pas attribuer à “” en soi

Un paresseux stockées propriété (voir le Langage de Programmation Swift livre, page 313) est plus approprié pour ce que vous essayez de faire ici.

lazy var managedObjectContext = createManagedObjectContext()

createManagedObjectContext() ne sera pas appelé jusqu'à ce que vous essayez d'accéder à la propriété pour la première fois (et uniquement la première fois).

Ajouter!! = )

//MARK: - Core Data stack

lazy var applicationDocumentsDirectory: NSURL = {
//The directory the application uses to store the Core Data store file. This code uses a directory named "com.YOURNAME_OTHERS.YOURAPP" in the application's documents Application Support directory.
    let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1] as NSURL
}()
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 = NSBundle.mainBundle().URLForResource("YOURAPP", withExtension: "momd")
return NSManagedObjectModel(contentsOfURL: modelURL)
}()
lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
//The persistent store coordinator for the application. This implementation creates and return 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
    var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("YOURAPP.sqlite")
var error: NSError? = nil
var failureReason = "There was an error creating or loading the application's saved data."
if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error: &error) == nil {
coordinator = nil
//Report any error we got.
        let dict = NSMutableDictionary()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
dict[NSLocalizedFailureReasonErrorKey] = failureReason
dict[NSUnderlyingErrorKey] = error
error = NSError.errorWithDomain("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 \(error), \(error!.userInfo)")
abort()
}
return coordinator
}()
lazy var managedObjectContext: NSManagedObjectContext? = {
//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
if coordinator == nil {
return nil
}
var managedObjectContext = NSManagedObjectContext()
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
//MARK: - Core Data Saving support

func saveContext () {
if let moc = self.managedObjectContext {
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
//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.
            NSLog("Unresolved error \(error), \(error!.userInfo)")
//abort()
        }
}
}