Why can't I set a dynamic property inside a nested function? - flutter

Question

I'm trying to create a function that can dynamically set the properties on an object like so:
void main() {
final obj = Item();
obj.update(5);
print(obj.xVal);
}
class ObjectBase {
void _setData(current, newValue) {
current = newValue;
print(current);
}
}
class Item extends ObjectBase {
int _x;
int get xVal => _x;
update(x) {
_setData(_x, x);
}
}
The print statement in _setData works fine, but it doesn't actually appear to change _x, even if it has been passed through. I expected that changing the reference here would update it everywhere.
So why isn't this working and is there a fix?
You can assume that I do have good reason to be calling _setData inside update rather than just implementing the functionality in update.
Update:
A real life example of what i'm trying to achieve
class ViewModel extends ChangeNotifier {
void _setDataFromDependency(current, newValue) {
if (!deepDynamicEquality(current, newValue)) {
current = newValue;
notifyListeners();
}
}
}
class ListScreenViewModel extends ViewModel {
int _localCount = 0;
List<int> _globalList;
ListScreenViewModel();
List<int> get globalList => _globalList;
int get localCount => _localCount;
incrementLocal() {
_localCount++;
notifyListeners();
}
void update(ListStore listStore) {
_setDataFromDependency(_globalList, listStore.globalList);
// if (!deepDynamicEquality(_globalList, listStore.globalList)) {
// _globalList = listStore.globalList;
// notifyListeners();
// }
}
}

Answer 1

An oversimplified workaround is to return the value from _setData . #julemand101 has already answered limitations.
class ObjectBase {
int _setData(current, newValue) {
current = newValue;
print('current: $current');
return current;
}
}
class Item extends ObjectBase {
int _x;
int get xVal => _x;
update(x) {
_x = _setData(_x, x);
}
}