Sequencing two actions together using an epic in redux-observable

Question

I am building an application with react-native using redux-observable. Right now I am struggling to do a simple decoration over two actions in redux-observable by using an epic. What I am trying to achieve is simply to map two actions to one.

The error I am getting is:

You provided an invalid object where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.

Here is the code I am using:

import { Observable } from 'rx';

export const startApplicationEpic = (action$: Observable) =>
  action$
    .ofType('START_APPLICATION')
    .flatMap(() =>
      Observable.of(
        { type: 'REGISTER_PUSH_NOTIFICATIONS'},
        { type: 'AUTHENTICATION_REQUEST' }
      )
    );
    
// index.js

store.dispatch({ type: 'START_APPLICATION' })

To me the RxJS code I am using is valid, and if epics are a stream than this should work, or is it only possible to dispatch a single action from an epic?

What line throws the error? Are you sure it's somewhere in the code you showed here? Also you probably want to import from rxjs and not rx. — martin
I too agree that is suspicious--are you using the v4 adapter (redux-observable-adapter-rxjs-v4) ? If not, you will definitely need to use v5 which is published to npm as rxjs not rx — jayphelps
Thank you martin, that was the issue. I needed to use rxjs instead of rx, which is a dependancy of redux-observable, then everything worked fine. I guess under the hood they quite some differences. — Deniss B.
@martin did you want to add that as an answer and he can accept it? :) — jayphelps

jayphelps jayphelps · Accepted Answer · 2017-08-29T18:20:12

It appears you're importing rx (which is v4) instead of rxjs (which is v5). So your code is providing a v4 Observable to the flatMap of a v5 Observable (redux-observable internals by default give you v5). The two versions cannot interop by default, but there are temporary interop layers. I admit this is all pretty confusing.

The best way to use v4 with redux-observable is to include the adapter we created for it redux-observable-adapter-rxjs-v4. If if you are using v4 on accident or it otherwise doesn't make a difference, definitely use v5 instead.

Once you fix that, the code as provided works as expected, without errors: https://jsbin.com/xiqigi/edit?js,console

Sequencing two actions together using an epic in redux-observable

1 Answers