Flutter merge two firestore streams into a single stream

Question

I simply want to perform an \'OR\' operation and get the both results of two queries into one stream.

Here\'s my code with a single stream

 StreamBui         


        

Answer 1

This should work.

//Change your streams here
    Stream<List<QuerySnapshot>> getData() {
        Stream stream1 = Firestore.instance.collection('list').where('id', isEqualTo: 'false').orderBy('timestamp').snapshots();
        Stream stream2 = Firestore.instance.collection('list').where('id', isEqualTo: 'true').orderBy('timestamp').snapshots();
        return StreamZip([stream1, stream2]);
      }


  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: StreamBuilder(
          stream: getData(),
          builder: (BuildContext context, AsyncSnapshot<List<QuerySnapshot>> snapshot1) {

            List<QuerySnapshot> querySnapshotData =  snapshot1.data.toList();

            //copy document snapshots from second stream to first so querySnapshotData[0].documents will have all documents from both query snapshots
            querySnapshotData[0].documents.addAll(querySnapshotData[1].documents);

            if (querySnapshotData[0].documents.isEmpty)
              return Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  Center(
                    child: CircularProgressIndicator(),
                  )
                ],
              );
            if (querySnapshotData[0].documents.length == 0)
              return const Center(
                child: Text(
                  "Not Available",
                  style: TextStyle(fontSize: 30.0, color: Colors.grey),
                ),
              );

            return new ListView(
                children: querySnapshotData[0].documents.map((DocumentSnapshot document){
                 // put your logic here. You will have access to document from both streams as "document" here
                  return new ListCard(document);
                }).toList()
            );
          }
      ),
    );
  }

Hope this helps!!!

Answer 2

I used RxDart package to combine two streams as shown below

RxDart - CombineLatestStream

final Stream<DocumentSnapshot> user = Firestore.instance
        .collection("users")
        .document(firebaseUser.uid)
        .snapshots();

    final Stream<QuerySnapshot> cards =
        Firestore.instance.collection("cards").snapshots();

    CombineLatestStream.list([user, cards]).listen((data) {
      add(LoadedHomeEvent(
        data.elementAt(0),
        data.elementAt(1),
      ));
    });

Answer 3

Well I am late, but just gonna put it out there.

You can add whereIn clause in your query like this:

Firestore.instance.collection("collection_name").where("field",whereIn:["false","true"]).snapshots();

Answer 4

I’m not sure why you’re using forEach and Observable.just().

You can just merge two firestore streams directly like:

Observable.merge([stream1, stream2]).pipe(combineStream);

Wherre stream1/2 is just your firestore snapshot.