call method
Implementation
@override
String? call(DateTime? value) {
if (value == null) return null;
if (min != null && value.isAfter(min!)) {
return 'Should be after ${formatDate(min)}';
}
if (max != null && value.isBefore(max!)) {
return 'Should be before ${formatDate(max)}';
}
return null;
}