Swift - 类型的值'（NSObject） - ＆gt; （） - ＆gt; NotesListViewController'没有成员堆栈？

Question

我编写自己的CoreDataStack文件，当我编译项目时，收到警告“Swift - 类型的值”（NSObject） - ＆gt;（） - ＆gt; NotesListViewController'没有成员堆栈？“

class NotesListViewController: UITableViewController, NSFetchedResultsControllerDelegate {

    var stack: CoreDataStack = CoreDataStack(modelName:"UnCloudNotesDataModel", storeName:"UnCloudNotes")

    lazy var notes: NSFetchedResultsController = { (_) -> NSFetchedResultsController<NSFetchRequestResult> in
        var request = NSFetchRequest<NSFetchRequestResult>(entityName: "Note")
        request.sortDescriptors = [NSSortDescriptor(key: "dateCreated", ascending: false)]
        var notes = NSFetchedResultsController(fetchRequest: request, managedObjectContext: self.stack.context, sectionNameKeyPath: nil, cacheName: nil)
        notes.delegate = self
        return notes
    }()