Fire multiple actions and wait for them to resolve RxJS / Redux Observables

Question

I have an action that I want to use to initialise my app, I want to create an epic for this action and then fire multiple other actions off the back of this, wait for them to all complete and there fire another action. I had a look at other questions and it's pretty similar to this one

I've tried this approach and for me, it doesn't work, it fires the APP_INIT action then but then fails to fire any of the other actions in the sequence. Is anyone able to help?

import { of } from 'rxjs';
import { mergeMap, zip, concat, mapTo } from 'rxjs/operators';
import { ofType } from 'redux-observable';
import { firstAction, secondAction } from 'actions';

export default function appInit (action$) {
  return (
    action$.pipe(
      ofType('APP_INIT'),
      mergeMap(() =>
        concat(
          of(firstAction()),
          of(secondAction()),
          zip(
            action$.ofType('ACTION_ONE_COMPLETE'),
            action$.ofType('ACTION_TWO_COMPLETE')
          ).mapTo(() => console.log('complete'))
        )
      )
    )
  );
}

Answer 1

Turns out my code was pretty much okay in the first instance, the main cause was that I was importing concat from rxjs/operators when I should have been importing from rxjs directly, it took me hours to realise but it now works.

Full code below for anyone that it might help.

import { of, concat, zip } from 'rxjs';
import { mergeMap, map, take } from 'rxjs/operators';
import { ofType } from 'redux-observable';

import { appInitialisationComplete, APP_INITIALISATION } from 'client/actions/app/app';
import { actionOne, ACTION_ONE_COMPLETE } from 'client/actions/action-one/action-one';
import { actioTwo, ACTION_TWO_COMPLETE } from 'client/actions/action-two/action-two';

/**
 * appInitialisationEpic
 * @param  {Object} action$
 * @return {Object}
 */
export default function appInitialisationEpic (action$) {
  return (
    action$.pipe(
      ofType(APP_INITIALISATION),
      mergeMap(() =>
        concat(
          of(actionOne()),
          of(actioTwo()),
          zip(
            action$.ofType(ACTION_ONE_COMPLETE).pipe(take(1)),
            action$.ofType(ACTION_TWO_COMPLETE).pipe(take(1))
          )
            .pipe(map(() => appInitialisationComplete()))
        )
      )
    )
  );
}