validate method

@override String? validate()

Implementation

@override
String? validate() {
  if (value.isEmpty) {
    return null;
  }
  RegExp exp = RegExp(r"^[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,6}$");
  if (!exp.hasMatch(value)) {
    return FV.buildMessage(customMessage ?? FV.url, attribute);
  }
  return null;
}