how can i get value instead of Instance of 'Future'

Question

I'm using flutter and I am trying to get a value from shared_preferences for firebase.

i checked my cord doesn't work and uid was " Instance of 'Future' ".

the solution i found was using setState but i can't use that because it's not in Widget build.

in this situation, how can i get value(uid) instead of Instance of 'Future'

class MyItemProvider with ChangeNotifier {
  String uid = '';
  Future<void> getUid() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    uid = await prefs.getString('uid')!;
  }
  late CollectionReference itemsReference;
  List<Item> items = [];
  List<Item> find_result = [];

  MyItemProvider({reference}) {
    getUid();
    itemsReference = reference ?? FirebaseFirestore.instance.collection(uid);
  }

...
...
...

i try to use setState i checked 'print(uid);' was Instance of 'Future'

score 0 · Answer 1 · answered Jun 07 '23 at 18:38

You have to do following things

String uid = '';
  Future<String> getUid() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    return await prefs.getString('uid')!;
  }
  late CollectionReference itemsReference;
  List<Item> items = [];
  List<Item> find_result = [];

  MyItemProvider({reference}) async {
    uid = await getUid();
    debugPrint('userId $uid');
    itemsReference = reference ?? FirebaseFirestore.instance.collection(uid);
  }

score 0 · Answer 2 · answered Jun 08 '23 at 00:42

0

You need to await your Futute function "getUid" since it is a type of Future where it is being called.

But you can further your knowledge in dart asynchronous programming, read this

answered Jun 08 '23 at 00:42

nifesi

80
7

score 0 · Answer 3 · answered Jun 08 '23 at 09:47

0

You can use then() method since it returns the value from Future

 MyItemProvider({reference}) {
    getUid().then((uid) {
        itemsReference = reference ?? FirebaseFirestore.instance.collection(uid);
    });
  }

answered Jun 08 '23 at 09:47

Sowat Kheang

668
2
4
12

Or you can do just like @Rohan Jariwala's answer – Sowat Kheang Jun 08 '23 at 09:50

how can i get value instead of Instance of 'Future'

3 Answers3