fetch method
Implementation
Future<void> fetch (
List<Property> properties,
Map<String, dynamic>? user_data,
) async {
if (isDirty() == false)
return;
if (isFetching() == true) {
while (isFetching() == true)
await Future.delayed(Duration(milliseconds: 100));
return;
}
startFetch();
await onFetch(properties.where((e)=>e.is_dirty == true).toList(), user_data);
endFetch();
}