angular rxjs: access parameter on http error inside pipe/concatMap?

Question

I'm currently using pipe and concatMap to chain multiple http requests like this:

onErrorResumeNext(from(ids))
    .pipe(
        delay(10),
        concatMap(id => get(id))
    )
    .subscribe(res => {
        if (res = emptydata) return id
});

The get function handles building the query string from an array of ids and also contains retry and catchError.

Now, the problem is I need to access the same id parameter if I get no data on the response object.

Any ideas?

After subscription. It's not really an http error because I do get a response. It's just an empty object. I have an if-else statement after subscription that can check for that. If true, I need to find which ID it was. — Jigno Alfred Venezuela
– Jigno Alfred Venezuela, Commented Sep 26, 2018 at 17:56
What do you mean by "after subscription?" You can't do anything after the subscription since it's asynchronous. You would have to handle it within the subscription callback. — Explosion Pills
– Explosion Pills, Commented Sep 26, 2018 at 18:27
Yes, the subscription callback once the response comes back. I've edited the question. I'm not sure if this might affect it, but the subscription happens in the component, however, the pipe is returned from a service. — Jigno Alfred Venezuela
– Jigno Alfred Venezuela, Commented Sep 26, 2018 at 18:33

Explosion Pills · Accepted Answer · 2018-09-27 11:50:52Z

1

concatMap (and other higher order Observable operators) take an optional result selector function (Note: this is deprecated) that takes the output value and input value arguments. This allows you to pass both to the stream (for example as an array):

onErrorResumeNext(from(ids))
    .pipe(
        delay(10),
        concatMap(id => get(id), (res, id) => ([res, id]))
    )
    .subscribe(([res, id]) => {
        // note that `return` does nothing here
        if (res == emptydata) return id
});

If get is an Observable, you could also return id in the context where you have access to it:

concatMap(id => get(id).pipe(
  map(res => res != emptydata ? res : id)
)

If get is not an array, you can use an Observable creation function such as from to turn it into an array.

edited Sep 27, 2018 at 11:50

answered Sep 26, 2018 at 19:20

Explosion Pills

192k56 gold badges341 silver badges417 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Jigno Alfred Venezuela Over a year ago

Will try this out. Thanks!

Jota.Toledo Over a year ago

Notice that the result selector was deprecated on most operators since v5/v6. Please consider this in your answer.

Explosion Pills Over a year ago

@Jota.Toledo I wasn't aware of the resultSelector deprecation; thank you for pointing that out. I don't know another way to handle this other than my other suggestion of working within the concatMap callback function context.

Jigno Alfred Venezuela Over a year ago

I read about the resultSelector and its deprecation. Did not really understood how/when to use it before. However, since it's working for me. I'd use it while I can.

Explosion Pills Over a year ago

@JignoAlfredVenezuela github.com/ReactiveX/rxjs/blob/master/docs_app/content/guide/v6/… explains how to migrate, and my second code example is specific to your case.

|

Collectives™ on Stack Overflow

angular rxjs: access parameter on http error inside pipe/concatMap?

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related