override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let reuseIdentifier = ...

    switch tableView.dequeueReusableCellWithIdentifier(reuseIdentifier, forIndexPath: indexPath) {
    case let cell as TableViewCell1:
        cell.label?.text = texts[indexPath.row]
        return cell

    case let cell as TableViewCell2:
        cell.label?.text = texts[indexPath.row]
        cell.button?.setTitle(texts[indexPath.row], forState: .Normal)
        return cell

    default:
        abort()
    }
}