如何在表格单元格中创建UITextField成为第一响应者？

class CustomTextField: UITextField {
    override func becomeFirstResponder() -> Bool {
        let result = super.becomeFirstResponder()
        if let tableView = superview as? UITableView, let indexPath = tableView.indexPathForRow(at: convert(CGPoint.zero, to: tableView)) {
            tableView.scrollToRow(at: indexPath, at: .middle, animated: true)
        }
        return result
    }
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "CustomCell", for: indexPath)
    let textField = CustomTextField()
    textField.frame = cell.contentView.bounds
    textField.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    textField.tag = indexPath.row
    textField.delegate = self
    cell.contentView.addSubview(textField)
    return cell
}

func textFieldDidBeginEditing(_ textField: UITextField) {
    if let tableView = textField.superview?.superview as? UITableView, let indexPath = tableView.indexPathForRow(at: textField.frame.origin) {
        tableView.scrollToRow(at: indexPath, at: .middle, animated: true)
    }
}

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    tableView.deselectRow(at: indexPath, animated: true)
    if let cell = tableView.cellForRow(at: indexPath), let textField = cell.contentView.viewWithTag(indexPath.row) as? CustomTextField {
        textField.becomeFirstResponder()
    }
}