Usage Example

enum EmailError {
  empty,
  not;

  @override
  String toString() {
    switch (this) {
      case empty:
        return 'emailEmpty';
      case not:
        return 'invalidFormatEmail';
      default:
        return 'invalidFormatEmail';
    }
  }
}

class EmailField extends FFormField<String, EmailError> {

  EmailField({required String value}) : super(value);

  @override
  EmailError? validator(value) {
    if (value.isEmpty) return EmailError.empty;
    return null;
  }
}