pattern function

ValidatorFn<String> pattern(
  1. RegExp regExp, {
  2. String? message,
})

Returns a validator that checks a String value against regExp.

Implementation

ValidatorFn<String> pattern(RegExp regExp, {String? message}) {
  return (value) {
    if (value == null || value.isEmpty) return null;
    if (!regExp.hasMatch(value)) {
      return message ?? 'invalid format';
    }
    return null;
  };
}