     
     private var isSavedArticlesEmpty: Bool {
         return savedArticlesViewController.editController.isCollectionViewEmpty
-    }
-    
-    private enum LeftButtonType {
-        case add
-        case none
-    }
-    
-    private var leftButtonType: LeftButtonType = .none {
-        didSet {
-            guard oldValue != leftButtonType else {
-                return
-            }
-            switch leftButtonType {
-            case .add:
-                navigationItem.leftBarButtonItems = [addReadingListBarButtonItem]
-            default:
-                navigationItem.leftBarButtonItems = []
-            }
-        }
     }
 
     private var isSearchBarHidden: Bool = false {

                savedArticlesViewController.editController.navigationDelegate = nil
                removeChild(savedArticlesViewController)
                addChild(readingListsViewController)
                leftButtonType = .add
                scrollView = readingListsViewController?.collectionView
                isSearchBarHidden = true
                activeEditableCollection = readingListsViewController

                savedArticlesViewController.editController.navigationDelegate = self
                readingListsViewController?.editController.navigationDelegate = nil
                savedDelegate = savedArticlesViewController
                isSearchBarHidden = isSavedArticlesEmpty
                scrollView = savedArticlesViewController.collectionView
                activeEditableCollection = savedArticlesViewController
