May 19, 2018
I want to send a couple of requests an update a progress after each one is successful. In the end, I want to dispatch success action.
const epic = action$ => action$.filter(action.fetchRequestStart).switchMap(action => Observable.range(1, repeatTimes) .mergeMap(() => Observable.from(fetchRequest).mergeMapTo( Observable.of(action.increaseProgress()) ) ) .concat(Observable.of(action.fetchRequestSuccess())) .catch(action => Observable.of(action.fetchRequestError())) )
This is a simple epic implementing this logic. How does it work? After I filter out the action that is interesting for me from a stream, I map through it using
switchMap so if user action dispatches the same action one more time during
Observable.range the pending operation will be canceled.
range works like intended - it will emit as many observables as I provide in
repeatTimes. Right after that, I’m using
mergeMap so I can add multiple observables - in my case, I only add one to dispatch action of
increasingProgress. In the end, I use
concat to emit action of success at the end of
range. If anything goes wrong I catch errors in
This is it for today! I was a quick blog post but you can email me with your feedback.