validateValue method
Implementation
@override
String? validateValue(String fieldName, value) {
if (value == null) return null;
if (value is! Map) {
return '[$fieldName] must be a Map of ${K.toString()},${V.toString()}';
}
for (var v in value.entries) {
if (v.key is! K || v.value is! V) {
return '[$fieldName] has invalid entries';
}
}
return null;
}