Stream helper for build_redux and flutter_build_redux

Getting Started with StreamMiddleware

Add action

In you action file add the action that you want to trigger the stream subscription. The payload of this action should be of type SubscriptionPayload. The type of SubscriptionPayload should be the type of payload you want to receive in the getStream method in the MiddlewareStreamHandler. It can also be of type Null if you don't want to receive anything. In the example we have a payload type of Duration witch is the interval at witch we emit a new value:

ActionDispatcher<SubscriptionPayload<Duration>> get timeStream;

Create the stream middleware

Create middleware

We can create the the middleware using the MiddlewareStreamBuilder and add the actions you've created on the previous step. Note that only actions with the payload type of SubscriptionPayload are accepted.

Middleware<AppState, AppStateBuilder, AppActions> getStreamMiddleware() {
  final MiddlewareStreamBuilder<AppState, AppStateBuilder, AppActions> builder =
      new MiddlewareStreamBuilder<AppState, AppStateBuilder, AppActions>();

  builder..add(AppActionsNames.timeStream, new TimeStreamHandler());

  return builder.build();

Add you action handler class

To handle the middleware action you need to create a class that extends MiddlewareStreamHandler<AppState, AppStateBuilder, AppActions, Payload, StreamType>.

The Payload is the type of the SubscriptionPayload<Payload> object you've added in the first step. In getStream you receive the payload you've passed when you called the triggering action.

The StreamType is the type of the object you stream produces, like Stream<StreamType>.

In the getStream method you need to return the stream you want to listen to. onData is called each time a new value was emitted. You can also handle errors and stream close using the other callbacks. You can also chose to cancel the stream on error by overriding the cancelOnError field, default is false.

class TimeStreamHandler extends MiddlewareStreamHandler<AppState, AppStateBuilder, AppActions, Duration, int> {
  static final Log log = new Log('TimeStreamHandler');

  Stream<int> getStream(Duration payload) {
    //initialize your stream here

  void onData(MiddlewareApi<AppState, AppStateBuilder, AppActions> api, ActionHandler next,
      Action<SubscriptionPayload<Duration>> action, int event) {
    //handle new data emited

  void onError(MiddlewareApi<AppState, AppStateBuilder, AppActions> api, dynamic error, StackTrace stackTrace) {

  void onDone(MiddlewareApi<AppState, AppStateBuilder, AppActions> api) {
  bool get cancelOnError => false;

Add the stream middleware to your store

You just add you stream middleware to you middleware list of your Store.

  final Store<AppState, AppStateBuilder, AppActions> store = new Store<AppState, AppStateBuilder, AppActions>(
    new AppState.initialState(),
    new AppActions(),
    middleware: <Middleware<AppState, AppStateBuilder, AppActions>>[

Start listening to the stream.

To start listening to the stream you can now call the action you've create. When you subscribe you must give the payload you want to receive in getStream method in the MiddlewareStreamHandler. In this way you can manually subscribe and unsubscribe from the stream.



Getting Started with StreamedStoreConnector

If you want to remain subscribed to the stream as long as the Widget is on screen then you can use the StreamedStoreConnector<StoreState, Actions, LocalState, Payload> witch automatically manages the subscription for you. This is a thin wrapper around the StoreConnector from the flutter_built_redux package.

There are two more overrides to make this work.

streamAction is the action that triggers the subscription

subscribePayload is the payload you would normally pass to the subscription action. Payload is the type of the SubscriptionPayload

class NowStreamConnector extends StreamedStoreConnector<AppState, AppActions, int, Duration> {
  static final Log log = new Log('NowStreamConnector');

  NowStreamConnector({@required this.builder, @required this.duration});

  final ViewModelBuilder<int> builder;

  final Duration duration;

  Duration get subscribePayload => duration;

  ActionDispatcher<SubscriptionPayload<Duration>> streamAction(AppActions actions) => actions.timeStream;

  int connect(AppState state) => state.now;

  Widget build(BuildContext context, int now, AppActions actions) {
    return builder(context, now);

The logger package is https://pub.dartlang.org/packages/flutter_logger