FPift在Swift中的控制器之间的Coredata对象

Question

我将View对象从ViewcontrollerA传递给ViewcontrollerB。但是输出是不同的。我无法弄清楚ViewcontrollerB中实体为空的原因。

我曾经在下面的代码中打印两个控制器中的Article对象。

  print(String(describing:listOfArticles))

  

输出

ViewcontrollerA。

  <Article: 0x600000281810> (entity: Article; id: 0xd00000000168001c <x-coredata://949275DD-E091-49E8-A0D0-2C362B616F97/Article/p90> ; data: <fault>)

ViewcontrollerB。

Optional(<Article: 0x600000283610> (entity: <null>; id: 0xd0000000000c0012 <x-coredata://949275DD-E091-49E8-A0D0-2C362B616F97/Article/p3> ; data: <fault>))

在ViewcontrollerB中，entity: <null>;始终为null。当我尝试使用该对象时它会崩溃。

推送ViewcontollerA代码： -

guard let viewArticelArray = topStories_presenter.fetchAllAritcleForTopStories(fetchedResultsController:fetchedResultsController) else {
    return
}
let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "NewsCollectionViewController") as! NewsCollectionViewController
vc.listArticle = viewArticelArray[0]
parentNavigationController!.pushViewController(vc, animated: true)

ViewcontollerB

 var listArticle :Article!

     override func viewDidLoad() {
            super.viewDidLoad()
            print(String(describing:listArticle))       
        }

FetchResultViewController代码：

 fileprivate lazy var fetchedResultsController: NSFetchedResultsController<TopStorie> = {
        // Create Fetch Request
        let moc = CoreDataHelper().managedObjectContext
        let fetchRequest: NSFetchRequest<TopStorie> = TopStorie.fetchRequest()
        // Configure Fetch Request
        fetchRequest.sortDescriptors = [NSSortDescriptor(key:"typeid", ascending: true)]
        fetchRequest.predicate = NSPredicate(format: "category contains[c]%@", self.title!)
        // Create Fetched Results Controller
        let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext:moc, sectionNameKeyPath:"typeid", cacheName: nil)
        // Configure Fetched Results Controller
        fetchedResultsController.delegate = self
        return fetchedResultsController
    }()