CODEWITHSUNDEEP
firebaseflutterdartgoogle-cloud-firestore
Param B.
Param B.

Reputation: 95

The getter 'document' was called on null. Stream<QuerySnapshots> documents are not getting returned

The defined Stream<QuerySnapshot>, i'm calling the uid from the class constructor

Stream<QuerySnapshot> get hotels {
    // print("$uid in stream");

    return ownerCollection.document(uid).collection("hotels").snapshots();
  }

Setting the StreamProvider

class Hotels extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final user = Provider.of<User>(context);

    return StreamProvider<QuerySnapshot>.value(
      value: DatabaseService(uid: user.uid).hotels,
      child: Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.orangeAccent,
          title: Text("My Hotels"),
        ),
        body: HotelList())
      );

Here's my screen which is accessing the Stream<QuerySnapshot> 

class HotelList extends StatefulWidget {
  @override
  _HotelListState createState() => _HotelListState();
}

class _HotelListState extends State<HotelList> {
  @override
  Widget build(BuildContext context) {

    final hotels = Provider.of<QuerySnapshot>(context);

    for(var doc in hotels.documents) {
      print(doc.data);
    }

     return Container();
  }
}

When i'm running it, it gives me the error: The getter 'documents' was called on null , Reciever : null

Please help, i wanna print the all documents from the subcollection "hotels".

Upvotes: 0

Views: 104

Answers (1)

Abion47
Abion47

Reputation: 24781

As I said in the comment, the error message "X was called on null" means that X isn't what is null, but whatever you called it on. In your case, this is the problem code:

final hotels = Provider.of<QuerySnapshot>(context);

for(var doc in hotels.documents) {
  print(doc.data);
}

The error is saying documents is getting called on null, which means hotel is null. That means that your provider fetching isn't working properly.

I haven't worked with the StreamProvider much, but if I had to guess it's because the first time your widget is built the source stream hasn't published any data yet, which makes sense as the source of the stream is an online service that needs time to connect and gather the data. This means there is no QuerySnapshot to return, and as such the Provider.of is returning null.

Normally you would fix this by giving the StreamProvider an initial value. Since the type is QuerySnapshot, though, I'm not sure what a sensical initial value would be other than, well, null. In that case, your only real option is to just handle the case where hotel is null.

final hotels = Provider.of<QuerySnapshot>(context);

if (hotels == null) {
  print('There is no data yet.');
  return Container();
}

...

Upvotes: 3

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