How to perform async calls inside streambuilder? - flutter

Question

I have an flutter app, which uses FirebaseAuth for authentication and Firestore for storing data. To store user profile (name, photo etc), I've created a separate collection in my firestore database.
So, once a user registers he is redirected to a screen where he can add his profile data. This data is again stored as a document.
I want to implement the same checks when the app is starting:
So, I display a splash screen and in the backend it checks,
Is the user logged in? If yes, proceed, else redirect him to the terms and conditions page.
Does the collection have user profile? If yes, proceed, else redirect him to a page where he can add his photo etc.
I was able to accomplish point 1, but I am not able to do the 2nd check.
Here's the code:
class SplashScreen extends StatelessWidget {
static final String id = 'splash_screen';
final Firestore _firestore = Firestore.instance;
#override
Widget build(BuildContext context) {
return StreamBuilder<FirebaseUser>(
stream: FirebaseAuth.instance.onAuthStateChanged,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.active) {
FirebaseUser user = snapshot.data;
if (user == null) {
return TermsAndConditions();
}
// Check if user profile has been created
return ChatsScreen();
} else {
return SplashScreenContent();
}
},
);
}
}
The commented line is where the code for checking user profile should go.
I tried the following:
_firestore.collection('users').where('id', isEqualTo: user.uid).snapshots().first.then( (value) {
if(value.documents.isEmpty) {
return ProfileScreen();
}
});
As I understand I cannot return the value to outer function from the callback. How can I achieve this

Answer 1

What you want to do is to show splash screen every time.
Then, inside splash screen, you can create the check.
call this function inside initState
void bootstrap() async {
var user = await FirebaseAuth.instance.currentUser();
if (user == null) {
Navigator.push(context,
MaterialPageRoute(builder: (context) => TermsAndConditions()));
return;
}
DocumentSnapshot userDoc =
await Firestore.instance.collection("users").document(user.uid).get();
if (!userDoc.exists) {
Navigator.push(
context, MaterialPageRoute(builder: (context) => ProfilePage()));
return;
}
Navigator.push(
context, MaterialPageRoute(builder: (context) => ChatsScreen()));
}
You can also add initial 2-3 seconds delay, else the splash screen can be too abruptly changed.
You can find many splash screen libraries in pub.dev that allow you to do this bootstraping.