BlogPost_20201112_4.swift

func toggleSelectedStateOfItem(at indexPath: IndexPath) {
    let item = dataSource.itemIdentifier(for: indexPath)!
    var snapshot = dataSource.snapshot()
    item.isSelected = !item.isSelected
    snapshot.reloadItems([item])
    dataSource.apply(snapshot)
}

let cellProvider: CellProvider = { (tableView, indexPath, item) -> UITableViewCell? in
    let cell = tableView.dequeueReusableCell(
        withIdentifier: cellIdentifier,
        for: indexPath) as! MenuItemTableViewCell
    cell.accessoryType = item.isSelected ? .checkmark : .none
    cell.textLabel?.text = item.name
    return cell
}