How to return an int from Firebase Realtime Database in Flutter

Question

int GetInitial(String roomID) {
    final dbRef =
        FirebaseDatabase.instance.reference().child(roomID).child("initial");
    db.child(roomID).child('initial').once().then((DataSnapshot snapshot) {
      print('Data : ${snapshot.value}');
      return int.parse(snapshot.value);
    });
    return 0;
  }

I'm trying to return the value of a child in my Firebase Realtime Database JSON tree, but it keeps giving me zero. I cannot access the value directly using once() as the return value is wrong. The output that I get from printing the value to the console is correct however, however it does not return int.parse(snapshot.value).

Solution

once() is asynchronous, the then() method will register callbacks to be called when this future completes. Therefore in your code 0 will always be returned since it is getting executed before the future is finishing.

To solve that, you can use async/await:

Future<int> GetInitial(String roomID) async {
    final dbRef = FirebaseDatabase.instance.reference().child(roomID).child("initial");
    final snapshot = await db.child(roomID).child('initial').once();
    print('Data : ${snapshot.value}');
    return int.parse(snapshot.value);
  }

Comments

[Admin]

I changed it to return snapshot.value() since int.parse() does not work on non-string values, and it returns a future<int>, which I am unable to convert to an int

[Peter Haddad]

you need to use futurebuilder widget to get the int value api.flutter.dev/flutter/widgets/FutureBuilder-class.html