validate method

@override String? validate(String? value)

Validates the given value and returns an error message if the value is invalid.

Implementation

@override
String? validate(String? value) {
  if (value == null) _getErrorMessage();
  if (value != null) {
    String? equalToText = useTrim ? equalTo.trim() : equalTo;
    String? text = useTrim ? value.trim() : value;
    if (!caseSensitive) {
      if (text.toLowerCase() != equalToText.toLowerCase()) {
        return _getErrorMessage();
      }
    } else {
      if (text != equalToText) {
        return _getErrorMessage();
      }
    }
  }
  return null;
}