validate method
Function to validate the form input. It takes a string and returns an String error message if the input is invalid or null if the input is valid.
Implementation
@override
String? validate(
BuildContext context,
String fieldName,
String? value,
) {
_isValid = true;
_shortErrorMessage = null;
_longErrorMessage = null;
for (final validator in _validators) {
final error = validator.validate(context, fieldName, value);
if (error != null) {
_isValid = validator.isValid;
_shortErrorMessage = validator.shortErrorMessage;
_longErrorMessage = validator.longErrorMessage;
return error;
}
}
return null;
}