Access Redux Store via Isolate

[ghost]

Hi,

I'm creating a chat app and would want to sync contacts on a different thread, than the main thread - using an isolate probably.

How can I connect to flutter store via an isolate?

[brianegan]

Hey there -- I'd generally handle this in the Middleware layer. Overall, Isolates are very restricted on what data can be sent back and forth. Unfortunately, Streams are one of those things that cannot be passed back and forth, and the Store contains a Stream. Therefore, it isn't possible to pass the Store itself from one Isolate to another.

Therefore, I'd recommend creating a Middleware that synced the Contacts on a separate isolate, and returns those contacts to the middleware when it's finished syncing. Then, the middleware can dispatch the results.

For more info on running heavy json parsing operations in a separate isolate, you can check out this recipe: https://flutter.io/cookbook/networking/background-parsing/

It would look something like this:

class Contact {
  final String name;

  Contact(this.name);
}

class ContactsReceivedAction {
  final List<Contact> contacts;

  ContactsReceivedAction(this.contacts);
}

class ContactsErrorAction {
  final Object error;

  ContactsErrorAction(this.error);
}

void isolateMiddleware(
  Store<AppState> store,
  dynamic action,
  NextDispatcher next,
) async {
  if (action is ClearCompletedAction) {
    try {
      // Use the `compute` function to make the network call / parse json in
      // a separate isolate.
      final contacts = await compute(fetchContacts, '');

      store.dispatch(ContactsReceivedAction(contacts));
    } catch (e) {
      store.dispatch(ContactsErrorAction(e));
    }
  }

  next(action);
}

List<Contact> fetchContacts(String _) {
  return [Contact('Brian')];
}

[brianegan]

Hey @adityasodhani -- did this help out?