Getting null on Query snapshot - firebase

Question

I ma getting a null return on a stream query. The funny thing is that data came through but on processing it to use it in the app it gets lost somewhere.I know i probably made a silly mistake somewhere yet i've been looking at this issue for three days now. Please help.
Here is the stream
Stream <SellerProfile> get sellerProfile {
return sellerProfileCollection.document(uid).snapshots()
.map(yieldSellerProfile);
}
SellerProfile yieldSellerProfile(DocumentSnapshot snapshot) {
print(snapshot.data['shopName']);
return SellerProfile(
shopName: snapshot.data['shopName'] ?? '',
phone: snapshot.data['phone']??'',
credit: snapshot.data['credit'] ?? '',
posts: snapshot.data['posts'] ?? '',
sales: snapshot.data['sales'] ?? '',
avatarUrl: snapshot.data['avatarUrl'] ?? '',
location:snapshot.data['location'] ?? '',
rating: snapshot.data['rating'] ?? '',
joinedDate: snapshot.data['joinedDate'] ?? '',
);
}
My idea is that after querying the stream sellerProfile i want to map it into a custom model to use it in the app.
As in the code, i print the snapshot.data['shopName'] before it is processed and i get the output
I/flutter ( 1008): Soko
which means the data arrives from firestore but as i try to access the data on my frontend i receive a null
Here is the frontend
Widget build(BuildContext context) {
final AuthService _auth = AuthService();
final user = Provider.of<User>(context);
return StreamBuilder<SellerProfile>(
stream: SellerDatabaseService(uid: user.uid).sellerProfile,
builder: (context, snapshot) {
SellerProfile profile=snapshot.data;
print(profile);
return Scaffold(
backgroundColor: Colors.white,
appBar: header(context,strTitle: "Profile"),
body: SingleChildScrollView(),
);
}
);
}
and here is the output when i try to print the profile
I/flutter ( 1008): null
Where am i going wrong? Thanks in advance!

Answer 1

I go the issue. I was trying to build the stream with stream builder instead of returning it from a provider.
So i changed this...
Widget build(BuildContext context) {
final AuthService _auth = AuthService();
final user = Provider.of<User>(context);
return StreamBuilder<SellerProfile>(
stream: SellerDatabaseService(uid: user.uid).sellerProfile,
builder: (context, snapshot) {
SellerProfile profile=snapshot.data;
print(profile);
return Scaffold(
backgroundColor: Colors.white,
appBar: header(context,strTitle: "Profile"),
body: SingleChildScrollView(),
);
}
);
}
To this...
return StreamProvider<BuyerProfile>.value(
value: BuyerDatabaseService(uid: user.uid).buyerProfile,
builder: (context, snapshot) {
BuyerProfile profile=Provider.of<BuyerProfile>(context);
if(profile!=null){
return Scaffold(...

Answer 2

You're not checking if the snapshot has data yet. Add a check for this with the hasData property of the AsyncSnapshot:
return StreamBuilder<SellerProfile>(
stream: SellerDatabaseService(uid: user.uid).sellerProfile,
builder: (context, snapshot) {
if(snapshot.hasError) {
return Text(snapshot.error.toString());
}
if(!snapshot.hasData) {//Check if the snapshot actually has data
return CircularProgressIndicator();
}
SellerProfile profile=snapshot.data;
print(profile);
return Scaffold(
backgroundColor: Colors.white,
appBar: header(context,strTitle: "Profile"),
body: SingleChildScrollView(),
);
}
);
Ideally you should also check if it hasError as well, and if you want more granular control over what to show, you could use the connectionState.