Fetching user name returns null at first time with Flutter Firebase

Question

I want to have the username (in Arabic) on the home page from firebase. When I ran the app the first time every time I turn on the emulator it returns null. But if I run it one more time/hot reload it is good. I tried using toString() but it also did not work.

Here is my code:

//user's info
  late User user;
  final _auth = FirebaseAuth.instance;
  late User signedInUser;
  var sex;
  var age;
  var name;

Future<void> _getData() async {
    FirebaseFirestore.instance
        .collection('users')
        .get()
        .then((QuerySnapshot querySnapshot) {
      querySnapshot.docs.forEach((doc) {
        if (doc["email"] == signedInUser.email) {
          name = doc['name'];
          age = doc['age'];
          sex = doc['sex'];
          print(doc['name']); //might delete
        }
      });
    });
  }

Widget build(BuildContext context) {
    return FutureBuilder(
        future: _getData(),
        builder: (context, snapshot) => snapshot.connectionState ==
                ConnectionState.waiting
            ? //more code

Text(
       '$name'.toString(),
        style: TextStyle(
                      ),
                    ) ```

Solution

Since _getData is an asynchronous method, it needs to return a Future, or it can use await, but in your code it does neither of those things.

For example, this now uses await to ensure the method only completes once the name is set:

Future<void> _getData() async {
  var querySnapshot = await FirebaseFirestore.instance
      .collection('users')
      .get();
  querySnapshot.docs.forEach((doc) {
    if (doc["email"] == signedInUser.email) {
      name = doc['name'];
      age = doc['age'];
      sex = doc['sex'];
      print(doc['name']); //might delete
    }
  });
}