How do you properly manage several genuinely separate distinct pieces of local state together within just one single StatefulWidget, such as both a loading flag and a genuinely separate list of fetched items?

Managing several genuinely separate distinct pieces of state together within just one single StatefulWidget simply involves declaring each individual piece as its own genuinely separate instance variable on that particular widget's own State class, and a single call to setState can genuinely update several of those separate pieces all together at once within that exact same one single callback, such as properly setting a loading flag back to false while also simultaneously assigning the genuinely newly fetched data, letting Flutter efficiently batch that entire combined set of related changes together into just one single overall rebuild rather than several genuinely separate individual ones.

bool _isLoading = true;
List<Item> _items = [];

void _loadItems() async {
  final items = await fetchItems();
  setState(() {
    _isLoading = false;
    _items = items;
  });
}