Flutter merge two firestore streams into a single stream - firebase

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
StreamBuilder(
stream: Firestore.instance
.collection('list')
.where('id', isEqualTo: 'false')
.orderBy('timestamp')
.snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData)
return Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Center(
child: CircularProgressIndicator(),
)
],
);
if (snapshot.data.documents.length == 0)
return const Center(
child: Text(
"Not Available",
style: TextStyle(fontSize: 30.0, color: Colors.grey),
),
);
return ListView.builder(
padding: EdgeInsets.all(5.0),
key: Key(randomString(20)),
itemCount: snapshot.data.documents.length,
itemBuilder: (BuildContext context, int index) {
return ListCard(snapshot.data.documents[index]);
},
);
}),
Instead of a single stream now I want to feed two stream to the same stream builder.
I tried StreamGroup but it's not working since Widgets rebuild
StreamGroup.merge([streamOne, streamTwo]).asBroadcastStream();
I tried followed method also
Stream<List<DocumentSnapshot>> searchResult() {
List<Stream<List<DocumentSnapshot>>> streamList = [];
Firestore.instance
.collection('room-list')
.where('id', isEqualTo: 'false')
.snapshots()
.forEach((snap) {
streamList.add(Observable.just(snap.documents));
});
Firestore.instance
.collection('room-list')
.where('id', isEqualTo: 'pending')
.snapshots()
.forEach((snap) {
streamList.add(Observable.just(snap.documents));
});
var x = Observable.merge(streamList)
.scan<List<DocumentSnapshot>>((acc, curr, i) {
return acc ?? <DocumentSnapshot>[]
..addAll(curr);
});
return x;
}
Here I get the error there should be at least a single stream to merge. Its because Observable.merge(streamList) is called before items are added to streamList.
I simply want to get the both results of two queries into one stream.

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’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.

Answer 3

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 4

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 5

I was also trying to combine two streams from firestore (as querying does not support OR) and went about it like this:
import 'package:rxdart/rxdart.dart';
Rx.combineLatest2(
StreamQuerySnapshot1, //a snapshot from firestore
StreamQuerySnapshot2, //another snapshot from firestore
(var stream1, var stream2) {
return [...stream1.docs, ...stream2.docs]; //Concatenated list
}
)
This will emit changes no matter which streams is changing in contrast to other solutions I found which support emits only if both streams have changes.

Answer 6

The best way I found is to use MergeStream from RxDart
Stream<QuerySnapshot> searchResult() {
final falseRoomStream = FirebaseFirestore.instance
.collection('room-list')
.where('id', isEqualTo: 'false')
.snapshots();
final pendingRoomStream = FirebaseFirestore.instance
.collection('room-list')
.where('id', isEqualTo: 'pending')
.snapshots();
return MergeStream([falseRoomStream, pendingRoomStream]);
}