authentication state changes return always null-CodePudding

I am trying to create a stream of my user modal based on the authenticate services of fire base.

create user object base on FirebaseUser:

 UnicoUser? _userFromFirebaseUser(User? user){
    if (user != null) {
      UnicoUser? _unicoUser;
      DatabaseService(uid: user.uid).getUserFromUserId().then((value){ _unicoUser = value; print("user id: "  value.uid);});
      return _unicoUser;
    }
    return null;
    }

create the auth change user stream:

  Stream<UnicoUser?> get unicoUser {
    return _auth.authStateChanges().map(_userFromFirebaseUser);
  }

the implement in the widget:

StreamBuilder(
          stream: AuthServices().unicoUser,
          builder: (context, AsyncSnapshot<UnicoUser?> snapshot) {
            if (snapshot.connectionState == ConnectionState.waiting){
              return const Loading();}
            else if(snapshot.hasData ){
              return LoggedInWrapper(currentUser: snapshot.data!,);}
            else if (snapshot.hasError){
              return const Center(child: Text("Something went wrong"),);}
            else {
              print("snapshot is: "   snapshot.data.toString());return const Authenticate();}
          },
        )

even if the user is authenticated and the unicouser object is not null the snapshot data is null.. output:

Performing hot reload...
Syncing files to device AOSP on IA Emulator...
Reloaded 0 libraries in 111ms.
I/flutter (22920): snapshot is: null
I/flutter (22920): user id: fnWyLWrCznQDSmZGr6kShpXSsK52

CodePudding user response：

The problem is your _userFromFirebaseUser function. Unfortunately, you cannot handle async values this way. The function returns before your _unicouser is set by then. You need to use an async function and await the result like this:

Future<UnicoUser?> _userFromFirebaseUser(User? user) async {
  if (user != null) {
    return await DatabaseService(uid: user.uid).getUserFromUserId();
  }
  return null;
}

Then you should be able to use it like this:

Stream<UnicoUser?> get unicoUser {
  return _auth.authStateChanges().asyncMap(_userFromFirebaseUser);
}