сохранение данных в основных данных перезаписывает все записи в swift

Question

У меня есть таблица, в которой отображается список животных. При нажатии на каждую ячейку (или животное) она перемещается к деталям животного и имеет кнопку сохранения.Всякий раз, когда я сохраняю информацию с использованием основных данных, все записи в основных данных перезаписываются последними обновленными данными.Я не уверен, в чем может быть причина.Ссылка на код взята из этого поста: Swift 3 IOS 9 и IOS 10 Core Data

Ниже приведен код

class CoreDataStack {

    static var applicationDocumentsDirectory: URL = {

        let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        return urls[urls.count-1]
    }()

    static 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(for: CoreDataStack.self).url(forResource: "DatabaseTest", withExtension: "momd")! // type your database name here..
        return NSManagedObjectModel(contentsOf: modelURL)!
    }()

    static 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: managedObjectModel)
        let url = applicationDocumentsDirectory.appendingPathComponent("DatabaseTest.sqlite") // type your database name here...
        var failureReason = "There was an error creating or loading the application's saved data."
        let options = [NSMigratePersistentStoresAutomaticallyOption: NSNumber(value: true as Bool), NSInferMappingModelAutomaticallyOption: NSNumber(value: true as Bool)]
        do {
            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
    }()

    static 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 = persistentStoreCoordinator
        var managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
        managedObjectContext.persistentStoreCoordinator = coordinator
        return managedObjectContext
    }()

static func getEntity<T: NSManagedObject>() -> T {
    if #available(iOS 10, *) {
        let obj = T(context: CoreDataStack.context)
        return obj
    } else {
        guard let entityDescription = NSEntityDescription.entity(forEntityName: NSStringFromClass(T.self), in: CoreDataStack.context) else {
            fatalError("Core Data entity name doesn't match.")
        }
        let obj = T(entity: entityDescription, insertInto: CoreDataStack.context)
        return obj
    }
}

    // MARK: - Core Data Saving support

    static 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()
            }
        }
    }

}

При нажатии на кнопку Сохранить, яНазовите этот код

   let animalObj: animalTable = CoreDataStack.getEntity()

        animalObj.Name = animalModel.Name
        animalObj.Type = animalModel.Type

    CoreDataStack.saveContext()

Не уверен, в чем проблема того, что он перезаписывает все данные в основных данных с последними сохраненными данными.