Cannot get result of first HTTP request using RxJS' switchMap

Question

I am trying to make 2 HTTP requests and in the first call I try to create a record and then according to its results (response from the API method) I want to execute or omit the second call that updates another data. However, although I can catch the error in catchError block, I cannot get the response in the switchMap method of the first call. So, what is wrong with this implementation according to teh given scenario? And how can I get the response of the first result and continue or not to the second call according to this first response?

let result;
let statusCode;

this.demoService.create(...).pipe(
    catchError((err: any) => { ... }),
    switchMap(response => {

    // I am trying to get the response of first request at here
    statusCode = response.statusCode;

    if(...){
        return this.demoService.update(...).pipe(
            catchError((err: any) => { ... }),
            map(response => {
            return {
                result: response
              }
          }
        )
      )}
    }
  ))
  .subscribe(result => console.log(result));

Answer 1

You can implement with iif

this.demoService
   .create(...)
   .pipe(
     // tap first to be sure there's actually a response to process through
     tap(console.log),

     // You can use any condition in your iif, "response.user.exists" is just a sample
     // If the condition is true, it will run the run the update$ observable
     // If not, it will run the default$
     // NOTE: All of them must be an observable since you are inside the switchMap
     switchMap(response => 
      iif(() => 
        response.user.exists, 
        this.demoService.update(response.id),    // Pass ID 
        of('Default Random Message')
      )
     ),
     catchError((err: any) => { ... })
   );

Answer 2

The question is still vague to me. I'll post a more generic answer to make few things clear

There are multiple things to note

1. When an observable emits an error notification, the observable is considered closed (unless triggered again) and none of the following operators that depend on next notifications will be triggered. If you wish to catch the error notifications inside the switchMap, you could return a next notification from the catchError. Something like catchError(error => of(error)) using RxJS of function. The notification would then be caught by the following switchMap.

2. You must return an observable from switchMap regardless of your condition. In this case if you do not wish to return anything when the condition fails, you could return RxJS NEVER. If you however wish to emit a message that could be caught by the subscriptions next callback, you could use RxJS of function. Replace return NEVER with return of('Some message that will be emitted to subscription's next callback');

import { of, NEVER } from 'rxjs';
import { switchMap, catchError, map } from 'rxjs/operators';

this.demoService.create(...).pipe(
  catchError((err: any) => { ... }),
  switchMap(response => {
    statusCode = response.statusCode;

    if (someCondition) {
      return this.demoService.update(...).pipe(  // emit `update()` when `someCondition` passes
        catchError((err: any) => { ... }),
        map(response => ({ result: response }))
      );
    }
    // Show error message
    return NEVER;               // never emit when `someCondition` fails
  }
)).subscribe({
  next: result => console.log(result),
  error: error => console.log(error)
});