private lazy var resultUnitsTextField: UITextField = {
    let textField = UITextField()
    textField.tintColor = .clear // 커서 색상 투명으로 변경
    textField.delegate = self
    return textField
  }()

extension ExchangerViewController: UITextFieldDelegate {
  func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    return false // 입력 불가
  }
}