How can you nest StreamBuilders in Flutter?

Question

I have 2 Streams that I need to combine to build a widget, but unlike other questions I have seen I need to nest my streams.

I have a stream that gets a collection

Answer 1

Try merging your streams with something like Observable.zip2(stream1,stream2,zipper) or Observable.combineLatest2(streamA, streamB, combiner).

For more info, check this post

Answer 2

I have done something similar simply using nested StreamBuilders. Depending on how you want your Widgets organized, you can create streams within the outer StreamBuilder. Based on your clarifying comments, this is one possibility:

@override
Widget build(BuildContext context) {

  var habits = Firestore.instance
    .collection("users")
    .document('VtL1sxOoCOdJaOTT87IbMRwBe282')
    .collection("habits")
    .snapshots();

  return StreamBuilder<QuerySnapshot>(
    stream: habits,
    builder: (context, snapshot) {

      if (!snapshot.hasData)
        return Text("Loading habits...");

      return ListView(children: snapshot.data.documents.map((document) {

        var query = Firestore.instance
          .collection("users")
          .document('VtL1sxOoCOdJaOTT87IbMRwBe282')
          .collection("habits")
          .document(document.documentID)
          .collection("history")
          .where('day', isGreaterThanOrEqualTo: start)
          .where('day', isLessThanOrEqualTo: end)
          .snapshots();

        return StreamBuilder<QuerySnapshot>(
          stream: query,
          builder: (context, snapshot) {

            if (!snapshot.hasData) return Text("Loading...");

            // right here is where you need to put the widget that you
            // want to create for the history entries in snapshot.data...
            return Container();
          },
        );
      }).toList());
    },
  );
}