Making first observable in chain optional

I currently have two API requests, where the first feeds into the second:

.get('/call1', )
.pipe(
switchMap(response => {
this.api.get('/call2', )


This works fine (though if there's a more appropriate way of doing it, I'd love to hear!). However, with some recent changes to my app, I realize in certain cases I have the data that call1 gets already stored, and thus can go straight to the second call, but I can't figure out how to do that. In other cases, within a switchMap, I've done something like:

call1

switchMap

if (condition)
return this.api.get('/call2');
else
return ObservableOf(cachedData);


How can I do something similar for the first call in a chain?

this.api.get('...').subscribe( (result) => whatever you want)

2 Answers
2

You can apply the condition in a separate function

getCall1()
.pipe(
switchMap(response => {
this.api.get('/call2', )


The function can decide where to get the data from and return an observable just like your example:

getCall1() : Observable<any>
if (condition)
return this.api.get('/call2');
else
return of(cachedData);



I'd recommend using some kind of caching layer or data store in your API layer. That way every time you call "this.api.get()" you can return an observable with the appropriate value if it's already been retrieved. We use the latest version of angular and do something similar while saving the values after API calls locally using the browsers local storage.

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