Question 184881 in Flutter Question posted in
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Flutter – how can i get value instead of Instance of 'Future<String>'

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’

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3

Answers


  1. 0

    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);
  }
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  2. 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

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  3. 0

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

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