         reloadEmptyState()
         
         // Present snack bar to allow undo
-        let snack = LPSnackbar(title: "Class deleted.", buttonTitle: "UNDO", displayDuration: 3.0)
+        let snack = LPSnackbar(title: "Class deleted.", buttonTitle: "UNDO", displayDuration: nil)
         snack.viewToDisplayIn = self.view
         snack.bottomSpacing = (tabBarController?.tabBar.frame.height ?? 0) + 12
         

        } else {
            performSegue(withIdentifier: .showPreviousDetail, sender: indexPath)
        }
    }
    
    override func tableView(_ tableView: UITableView, editActionsForRowAt indexPath: IndexPath) -> [UITableViewRowAction]? {

    private func registerNotifications(for results: Results<Class>, in section: Int) {
        let notification = results.addNotificationBlock { [weak self] (changes) in
            guard let tableView = self?.tableView else { return }
            guard !(self?.searchController.isActive ?? false) else {
                tableView.reloadData()
                return
            }
            
            switch changes {
                
