ChangeNotifier dispose model too early - firebase

Question

I am use Firestore transaction for avoid race condition of add more than 1 user to chat. If transaction timeout, I show error dialog.
But when I move this logic to Model2 with ChangeNotifier (and Provider) it now show error:
Unhandled Exception: A Model2 was used after being disposed. Once you
have called dispose() on a Model2, it can no longer be used.
(No issue with Firestore transaction. This is expected):
PlatformException(9, Transaction failed all retries.: Every document
read in a transaction must also be written in that transaction., null)
It seem ChangeNotifier is call dispose() too early?
This mean it not allow me to handle error of race condition because it is already dispose.
Model:
class Model2 extends ChangeNotifier {
...
bool userAdded;
Future<bool> addUser() async {
try {
await Firestore.instance.runTransaction((transaction) async {
DocumentSnapshot chatRoomDocSnapshot =
await transaction.get(chatRoomDocRef);
bool userInChat = await chatRoomDocSnapshot[‘userInChat'];
if (userInChat == false) {
await transaction.update(chatRoomDocSnapshot.reference, {
‘userInChat': true,
});
}
});
await chatUserRef.setData({
‘User’: user,
});
userAdded = true;
notifyListeners();
} catch (e) {
print(e);
userAdded = false;
notifyListeners();
}
return userAdded;
}
Provider (in stateful widget):
fetchData();
return ChangeNotifierProxyProvider<Model1, Model2>(
initialBuilder: (_) => Model2(),
builder: (_, model1, model2) => model2
..string = model1.string,
),
child: Consumer<Model2>(
builder: (context, model2, _) =>
...
await model2.addUser();
...
Anyone know solution?
Thanks!
Update:
Issue is not throw if I remove fetchData(); from build method before ChangeNotifierProxyProvider .
But why is this fix the issue?

Answer 1

Going through the comments, it's likely that calling fetchData() rebuilds the entire screen - calling the dispose() method. If you're still having issues, I suggest providing logs and the code inside fetchData() for better context.