TableView的搜索栏不工作

我试图在TableView中添加一个搜索栏,它用CoreData存储数据。但是当我尝试搜索时,TableView没有更新。我认为fetch正在工作,但表没有更新。

func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
    if searchText.isEmpty {
        return
    }
    else {
        let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

        let sRequest: NSFetchRequest<Note> = Note.fetchRequest()
        sRequest.predicate =  NSPredicate(format: "SELF.title CONTAINS[cd] %@", searchText)
        sRequest.sortDescriptors = [NSSortDescriptor(key: "date", ascending: true)]

        let fetchedResultsController = NSFetchedResultsController(fetchRequest: sRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
        print(sRequest)

        do {
            try fetchedResultsController.performFetch()

        } catch {
            fatalError("Failed to fetch entities: \(error)")
        }

        self.mainTable.reloadData()
    }
    return
}


 func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell:UITableViewCell = mainTable.dequeueReusableCell(withIdentifier: "prototypeCell")!

    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
    let tableRequest: NSFetchRequest<Note> = Note.fetchRequest()
    tableRequest.sortDescriptors = [NSSortDescriptor(key: "date", ascending: false)]

    var fetchedResultsController = NSFetchedResultsController(fetchRequest: tableRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)

    do {
        try fetchedResultsController.performFetch()
    } catch {
        fatalError("Failed to fetch entities: \(error)")
    }

    let noteCell = fetchedResultsController.object(at: indexPath)
    cell.textLabel?.text = noteCell.title!

    let formatter = DateFormatter()
    formatter.dateFormat = "d.M.y, HH:mm"
    let dateString = formatter.string(from: noteCell.date! as Date)
    cell.detailTextLabel?.text = dateString

    return cell
}