Question 369184 in Flutter Question posted in
The official Flutter documentation can be found here.

ObservableStream<List<Type>> convert to List and/or ObservableList<Type> Flutter Mobx

I have setup a sqlite stream from Drift: Stream<List> into my @oberservable class. I can make it an OberserableStream, but I dont understand how to get the list from the stream.

My question is how can I get the list from the ObservableStream and make it an ObservableList or make it an ObeservableList directly from Stream?

Here’s what I got wrong so far. I have tried many permutations of this but IDE keeps telling me that its wrong type, wrong .map, wrong <whatever>

@observable  
ObservableList<TodoDrift> streamTodos() {
    ObservableStream<List<TodoDrift>> list = stObv.asObservable();
    List<TodoDrift> prod = list.map(
            (e) {
               return e.done != true;
              });
    return prod.asObservable();
    // return Future.wait(olStream);
  }

Thank you!

FWIW. I also have a Future<List> from Drift and that works fine, I can get the list from there, so that works and I know the data is there.

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    based on @pskink question, Here is the working code.

    State (mobx):

    //pulling from drift .watch() sqlite
@observable
  Stream<List<TodoDrift>> stObv = _db.streamTodos();

    Display:

      const TodoListView({super.key});

  @override
  Widget build(BuildContext context) {
    final list = TodoDriftList(); //access mobx state class/store

    return StreamBuilder(
        stream: list.stObv, //@observed stream  returned from drift .watch() query
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            return ListView.builder(
                itemCount: snapshot.data!.length,
                shrinkWrap: true,
                itemBuilder: (_, index) {
                  return Observer(
                      builder: (_) {
                        final item = snapshot.data![index];
                        return Text(item.description); //strictly for testing output
                      }
                  );
                }
            );
          } else {
            return const CircularProgressIndicator();
          }
        }
    );
  }
}

  2. 0

    answering your original question: this is how you could do that:

    ObservableList<int> streamToObservableList(Stream<List<int>> stream) {
  final list = ObservableList<int>();
  stream.listen((value) => list..clear()..addAll(value));
  return list;
}

    BUT, this is really useless to do that since you already have ObservableStream which you can directly use inside Observer widget:

    ObservableStream<List<int>> stream = ...

@override
Widget build(BuildContext context) {
  return Observer(
    builder: (_) {
      List<int>? value = stream.value;
      print('stream value: $value');
      // use `value` for building your widget tree
      return ...;
    },
  );
}
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search