validateCreditCardNumber function

String? validateCreditCardNumber(
  1. String? value
)

Validates a Credit Card Number. Returns null if valid, or an error message string if invalid.

Implementation

String? validateCreditCardNumber(String? value) {
  if (value == null || value.isEmpty) {
    return 'Please enter a credit card number';
  }
  // This is a basic Luhn algorithm check
  if (!_isValidCreditCard(value)) {
    return 'Enter a valid credit card number';
  }
  return null;
}