redux-observable, How to do an operator like promise.all()? - redux-observable

Question

I have two async requests, want to write a epic do the job like promise.all()
const fetchData1 = () => (action$: ActionsObservable<any>, store: any) => (
ajax.getJSON('../../mockData/promiseAll/data1.json').map((data: any) => {
return requestData1Success(data);
})
);
const fetchData2 = () => (action$: ActionsObservable<any>, store: any) => (
ajax.getJSON('../../mockData/promiseAll/data2.json').map((data: any) => {
return requestData2Success(data);
})
)
const requestAllDataEpic = (action$: ActionsObservable<any>, store: any) => {
return action$.ofType(t.REQUEST_ALL_DATA)
.map((action) => action.payload)
.switchMap((names: string[]) => {
console.log(names);
return Observable.forkJoin([
fetchData1()(action$, store),
fetchData2()(action$, store)
])
.map((results: any[]) => {
const [action1, action2] = results;
requestData1Success(action1);
requestData2Success(action2);
});
});
};
But when I dispatch the action, the console give me an error:
Uncaught TypeError: Cannot read property 'type' of undefined
I think the reason is I do not give the middleware an action object, but undefined.
How can I do this correctly?

Answer 1

In the provided example, you are not actually returning your two actions, you're returning nothing:
.map((results: any[]) => {
const [action1, action2] = results;
// v----- not returning either of these
requestData1Success(action1);
requestData2Success(action2);
});
map can't used to emit two actions sequentially because it's 1:1 not 1:many (mergeMap, switchMap, concatMap, etc are 1:many). However, in your example you are already converting the responses to the actions inside your fetchData helpers--doing it again would wrap an action inside another action, not what you want. This looks like a bug when you were refactoring.
Other than that, it's actually not clear what you intended to do. If you have further questions you'll need to describe what you want you'd like to achieve.