Flutter Futurebuilder not returning anything - asynchronous

Question

I have a Futurebuilder in flutter, but it never returns anything.
As you can see below, I have a Futurebuilder that calls a method called getGamesLost. If there is no data, it will show a loading indicator.
FirestoreUserProfile firestoreUserProfile = new FirestoreUserProfile();
#override
Widget build(BuildContext context) {
return FutureBuilder(
future: firestoreUserProfile.getGamesLost(),
builder: (BuildContext context, AsyncSnapshot<int> userProfileData) {
if(userProfileData.hasData) {
print(userProfileData);
}
else {
return Styling.loadingIndicator;
}
}
);
My problem is that there is never data. Below is the getGamesLost method.
Future<int> getGamesLost() async {
return await firestoreCollectionReference
.document(FirebaseUserData.currentFirebaseUser.email)
.snapshots().forEach((userData) {
return userData.data[describeEnum(fieldNames.profile)][describeEnum(fieldNames.gamesLost)];
});
}
For some reason the getGamesLost that is called by the futurebuilder never finishes. I can print the value of userData just before the last return, which means there actually is data returning from firebase, but it is as if the method never actually returns and the futurebuilder just keeps waiting.

Answer 1

It's because you are using a stream returned by snapshots() to get data and iterating it. This stream stays alive and listens to any realtime data updates. The forEach function here would give you a Future, but it completes only when the Stream returned by snapshots() completes. Hence, the Future never completes.
If you just want the value form the document, just use it like.
// The `get` method instead of `snapshots` just fetches the doc at this instance and would not listen for updates
Future<int> getGamesLost() async {
return await firestoreCollectionReference
.document(FirebaseUserData.currentFirebaseUser.email)
.get()
.then((DocumentSnapshot userData) {
return userData.data[describeEnum(fieldNames.profile)]
[describeEnum(fieldNames.gamesLost)];
});
}
Hope that helps!