Flutter-Firebase await return after stream.listen() finish

Question

Flutter Stream Issue I am trying to filter my database query by geohash, so I'm using Geoflutterfire, which returns a Stream. I tried to convert data from each DocumentSnapshot inside Stream<List<>> into a List. It works, but the problem is that the return happens before the actual finish of the stream.listen(). How can I delay the return to return the stream.listen result? I tried using await for(...), but it errors.

import 'dart:async';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter_redux/flutter_redux.dart';
import 'package:geoflutterfire/geoflutterfire.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_storage/firebase_storage.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:uerto/models/index.dart';

class SearchApi {
  const SearchApi({required FirebaseAuth auth, required FirebaseFirestore firestore, required FirebaseStorage storage, required Geoflutterfire geo})
      : _auth = auth,
        _firestore = firestore,
        _storage = storage,
        _geo = geo;

  final FirebaseAuth _auth;
  final FirebaseFirestore _firestore;
  final FirebaseStorage _storage;
  final Geoflutterfire _geo;

  Future<List<AppClient>> getClientList(LatLng location, String category, String subCategory, double radius, int limit) async{

    final List<AppClient> newResult = <AppClient>[];
    final GeoFirePoint center = _geo.point(latitude: location.latitude, longitude: location.longitude);
    final Query<Map<String, dynamic>> collectionReference = _firestore.collection('London$category/$subCategory/UID').limit(limit);
    const String field = 'position';
    final Stream<List<DocumentSnapshot<Map<String, dynamic>>>> stream = _geo.collection(collectionRef: collectionReference).within(center: center, radius: radius, field: field);
    // ignore: always_specify_types
    stream.listen((List<DocumentSnapshot> documentList) {
      // ignore: always_specify_types, avoid_function_literals_in_foreach_calls
      documentList.forEach((DocumentSnapshot document) async {
        ///print(document.data());
        final SearchUid searchUid = SearchUid.fromJson(document.data());
        //print(searchUid.uid);
        final DocumentSnapshot<Map<String, dynamic>> client = await _firestore.collection('clients').doc(searchUid.uid).get();
        final AppClient clientData = AppClient.fromJson(client.data());
        print(clientData);
        newResult.add(clientData);
      });
    });
    await for(List<DocumentSnapshot> documentList in stream){
      return newResult;
    }

  }
}

Solution 1

So you can try using .onDone after stream. So if the stream ends, onDone block will run.

 stream.listen((List<DocumentSnapshot> documentList) {

}).onDone((){
 //run here
});

Solution 2

you don't need a listen to get only the first-time data from the stream.

After initializing your stream, do following things:

List<DocumentSnapshot> documentList = await stream.first;
// Do your operations here
return newResult;

Comments

[Chetan Goyal]

Do you want to return only the first result from your stream?

[FLTY]

@ChetanGoyal yes, exactly

[Chetan Goyal]

okay. I am giving an appropriate answer for it now.

[FLTY]

thanks for your time!

[Chetan Goyal]

No problem. I have posted an answer. Let me know if you face any other problem while using it.

[FLTY]

its still the same error

[FLTY]

Well i changed my code with your and its still the same problem

[Chetan Goyal]

@FLTY I have edited my answer. Is it still not working?

[FLTY]

no it doesnt work either.. i have added await before you told me (cause an error popped)..

[Chetan Goyal]

Can you please show the error you received?

[Toto]

Please post your data as text, not image.