CODEWITHSUNDEEP
firebaseflutterdartgoogle-cloud-firestore
user2393256
user2393256

Reputation: 1150

Nested Futures for FutureBuilder

I have a FutureBuilder widget that should wait for data from a firestore collection.

class MyScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: calendarQuery.getCalendarEntry(dateString),
      builder: (BuildContext context, AsyncSnapshot snap) {
        if (snap.hasData) {
          List<Events> recipe = snap.data;
          return Scaffold(
            appBar: AppBar(
              title: Text("Events"),
            ),
            body: Column(
              children: <Widget>[
                ...,
              ],
            ),
          );
        } else {
          return LoadingScreen();
        }
      },
    );
  }
}

I retrieve a list of events and then for each event I need to fetch some additional details. I tried to do nested Futures and came up with the code below. It generates a Future<Iterable<Future<Detail>>> which ends up as MappedListIterable<DocumentSnapshot,Future<Recipe>> in snap.data and i cannot handle it.

class CalendarQuery<T> {
  ...

  Future<Iterable<Future<Detail>>> getCalendarEntry(String date, String type) async {
    return await ref
        .where("date", isEqualTo: date)
        .getDocuments()
        .then((data) {
      return data.documents.map((doc) => Document<Details>(path: 'detailCollection/${doc.data["Event"]["SomeId"]}')
                .getData());
    });
  }
}

I think I went wrong here at some points with handling the futures and there is probably a proper way to do this.

Does someone know a way to refactor getCalendarEntry so that it returns a Future<List<T>>? Or maybe there is a better approach to solve this?

Upvotes: 0

Views: 742

Answers (1)

Ovidiu
Ovidiu

Reputation: 8714

You can use Future.wait to create a Future that completes once all Futures from an Iterable have completed.

In your scenario, you would replace return await ref with return Future.wait(ref and a closing bracket where needed, to create a Future that waits for all Details to be retrieved.

Upvotes: 1

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