如何从Firebase身份验证获取用户ID作为字符串？

Question

I'm trying to insert data to firestore with the authenticated user id as the document id but i got null from the parameter.

Please take a look at my script.

void didChangeDependencies() {
  uid = '';
  super.didChangeDependencies();
}

Future _fetchUID() async {
  var auth = AuthProvider.of(context).auth;
  return await auth.getCurrentUser().then((user) => _uid = user.uid);
}

_validateAndSubmit() async {
  setState(() {
    _errorMessage = '';
    _isLoading = true;
  });

  if (_validateAndSave()) {
    try {
      _fetchUID();
      await Report.create(_uid, _suspectName, _plateNumber, _civilizationId,
          _drivingLicenseId, _clause, _description);
      return Navigator.of(context).pop();
    } catch (e) {
      setState(() {
        _isLoading = false;
        _errorMessage = e.message;
      });
      print(_errorMessage);
      throw Exception(e);
    }
  }
}

In this method below you can see that I have already tried to set the _uid , but I still cannot get the _uid value.

Future _fetchUID() async {
  var auth = AuthProvider.of(context).auth;
  return await auth.getCurrentUser().then((user) => _uid = user.uid);
}

This is how the getCurrentUser() method looks like.

Future<FirebaseUser> getCurrentUser() async {
  FirebaseUser user = await _firebaseAuth.currentUser();
  return user;
}

Am I doing it wrong?

Answer 1

First of all, you mixed the Future.then syntax and the async await syntax.
You should probably write your method this way:

void _fetchUID() async {
  var auth = AuthProvider.of(context).auth;
  _uid = (await auth.getCurrentUser()).uid;
}

If _uid is still null for you after calling _fetchUID this way, then you are simply not signed in, meaning that there is no FirebaseUser as you first need to sign in.

In your _validateAndSubmit method, you also first need to await your _fetchUID call, otherwise it will pass _uid before it has been assigned a value.

...
try {
  await _fetchUID();
  await Report.create(_uid, ..);
  ...