Combine Firebase DB Streams with RxDart - firebase

Question

I am attempting to combine two streams using RxDart and display the stream within a ListView.
I modeled this technique based on this post How do I join data from two Firestore collections in Flutter?, however, when I run this code, I am returning an empty dataset.
Any help would be greatly appreciated!
import 'package:rxdart/rxdart.dart';
class _HomeScreenState extends State<HomeScreen> {
Stream<List<CombineStream>> _combineStream;
String currentUserId = 'id12345'
#override
void initState() {
super.initState();
_combineStream =
usersChatsRef.child(currentUserId).onValue.map((userChatStream) {
return (userChatStream.snapshot.value).map((f) {
Stream<UsersChats> uDetail =
f.map<UsersChats>((node) => UsersChats.fromMap(node));
Stream<Chat> sDetail = chatsDetailsRef
.child(f.key)
.onValue
.map<Chat>((node2) => Chat.fromMap(node2.snapshot.value));
return Rx.combineLatest2(
uDetail, sDetail, (u, s) => CombineStream(u, s));
});
}).switchMap((streams) {
return (streams.length) > 0
? streams.combineLatestList(streams)
: streams.just([]);
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: StreamBuilder(
stream: _combineStream,
builder:
(BuildContext context, AsyncSnapshot<List<CombineStream>> snap) {
if (snap.hasData && !snap.hasError) {
return ListView.builder(
itemCount: snap.data.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(snap.data[index].combineUserChats.id),
subtitle: Text(myChats[index].combineUserChats.id),
);
},
);
} else {
return Center(child: Text("No data"));
}
},
),
);
}
}
class CombineStream {
final UsersChats combineUserChats;
final Chat combineChat;
CombineStream(this.combineUserChats, this.combineChat);
}
class Chat {
String id;
String name;
Chat({String id, String name}) {
this.id = id;
this.name = name;
}
factory Chat.fromMap(Map data) {
return Chat(
name: data['name'] ?? '');
}
}
class UsersChats {
String id;
String lastUpdate;
UsersChats(
{this.id,
this.lastUpdate});
factory UsersChats.fromMap(MapEntry<dynamic, dynamic> data) {
return UsersChats(
id: data.key ?? '',
lastUpdate: data.value['lastUpdate'] ?? '');
}
}