How to wait on / yield to multiple actions in single redux observable epic? - redux-observable

Question

I have a redux Saga that runs three different actions every time 'WATCHLIST_FETCH_REQUEST' is dispatched:
function* watchFetchWatchlist() {
yield takeLatest('WATCHLIST_FETCH_REQUEST', fetchWatchlist);
}
function* fetchWatchlist() {
const activity = 'ACTIVITY_FETCH_WATCHLIST';
yield put(
addNetworkActivity(activity) // Action 1: enables a global loading indicator before request is made
);
const { response, error } = yield call(
api.fetchWatchlist // make an API request
);
yield put(
removeNetworkActivity(activity) // Action 2: removes the above global loading indicator after request completes
);
if (response) {
yield put(
updateUserWatchlist(response) // Action 3a: updates Redux store with data if response was successful
);
} else {
yield put(
watchlistFetchFailed(error) // Action 3b: updates Redux store with error if response failed
);
}
}
The flow of this saga is synchronous in nature. Action 1 must run first to set the global loading state for the app. Action 2 must run after Action 1 and after the API response comes back to remove the global loading state when the network activity is finished.
I'm pretty new to redux-observable but I have been digging around a lot trying to figure out how to convert this saga into an epic. The two goals here:
Perform actions sequentially, one after the other, as opposed to running in parallel
Perform these actions / flow in a single epic (kicks off when type: 'WATCHLIST_FETCH_REQUEST' is fired)
How do you achieve this with redux-observable? Thanks!

Answer 1

I found the answer to my question by piecing together parts of the conversation here: https://github.com/redux-observable/redux-observable/issues/62
I ended up with something along the lines of:
import { concat as concat$ } from 'rxjs/observable/concat';
import { from as from$ } from 'rxjs/observable/from';
import { of as of$ } from 'rxjs/observable/of';
export const fetchWatchlistEpic = (action$) => {
const activity = 'ACTIVITY_FETCH_WATCHLIST';
return action$.ofType('WATCHLIST_FETCH_REQUEST')
.switchMap(() =>
concat$(
of$(addNetworkActivity(activity)),
from$(api.fetchWatchlist())
.map((data) => Immutable.fromJS(data.response))
.switchMap((watchlist) =>
of$(
updateUserWatchlist(watchlist),
removeNetworkActivity(activity),
)
)
)
);
};
concat and of seem to be the go-to operators when trying to run multiple actions in sequence.