isValidPIN static method

String? isValidPIN(
  1. String? pin, {
  2. int length = 4,
})

Validates PIN (typically 4-6 digits)

Implementation

static String? isValidPIN(String? pin, {int length = 4}) {
  if (pin == null || pin.isEmpty) {
    return 'Please enter your PIN.';
  }

  if (pin.length != length) {
    return 'PIN must be $length digits.';
  }

  final numericRegExp = RegExp(r'^\d+$');
  if (!numericRegExp.hasMatch(pin)) {
    return 'PIN must contain only numbers.';
  }

  return null;
}