required method
FormFieldValidator
that requires the field have a non-empty value.
Implementation
static FormFieldValidator required({
String errorText = "This field cannot be empty.",
}) {
return (valueCandidate) {
if (valueCandidate == null ||
((valueCandidate is Iterable ||
valueCandidate is String ||
valueCandidate is Map) &&
valueCandidate.length == 0)) {
return errorText;
}
};
}