Merge Firestore streams using rxDart

Question

I am trying to merge two streams from Firestore into one stream using RxDart, but it's only returning results of one stream

Stream getData() {
    Stream stream1 = Firestore.instance.collection('test').where('type', isEqualTo: 'type1').snapshots();
    Stream stream2 = Firestore.instance.collection('test').where('type', isEqualTo: 'type2').snapshots();
    return Observable.merge(([stream2, stream1]));
}

Solution 1

Depending on your use case, you might not need RxDart to do this. If you just want to have two Firestore streams merged to one Dart Stream you can use StreamZip from the dart:async package.

import 'dart:async';     

Stream<List<QuerySnapshot>> getData() {
  Stream stream1 = Firestore.instance.collection('test').where('type', isEqualTo: 'type1').snapshots();
  Stream stream2 = Firestore.instance.collection('test').where('type', isEqualTo: 'type2').snapshots();
  return StreamZip([stream1, stream2]).asBroadcastStream();
}

Solution 2

You can use mergeWith to get one Stream from two seperate streams using RxDart like below,

 Stream getData() {
    Stream stream1 = Firestore.instance.collection('test').where('type', isEqualTo: 'type1').snapshots();
    Stream stream2 = Firestore.instance.collection('test').where('type', isEqualTo: 'type2').snapshots();
    return stream1.mergeWith([stream2]);
  }

Comments

[Rémi Rousselet]

You may want to use combineLatest instead.

[Rémi Rousselet]

see stackoverflow.com/questions/51930918/…

[Arinzehills]

please how can i then access this data