isValid method

@override String? isValid(BuildContext context, String? value)

Validates if the value is less than or equal to maxValue.

Returns null if the value is valid, otherwise returns the error message.

Implementation

@override
String? isValid(BuildContext context, String? value) {
  if (value == null || value.isEmpty) return null;

  final numValue = num.tryParse(value);
  return numValue == null || numValue <= maxValue
      ? null
      : errorMessage ??
          defaultMessage[Localizations.localeOf(context).languageCode] ??
          defaultMessage['en'];
}