TypeError: You provided an invalid object where a stream was expected. You can provide an Observable, Promise, Array, or Iterable

Question

I am trying to map from a service call but getting an error. Looked at subscribe is not defined in angular 2? and it said that in order to subscribe we need to

Answer 1

I had the same issue caused by importing the internal version of 'takeUntil' instead of the operators Change

import { takeUntil } from 'rxjs/internal/operators/takeUntil';

to

import { takeUntil } from 'rxjs/operators';

This happen also for other operators

Answer 2

In my case in Angular-5, service file was not imported from which i was accessing the method and subscribing the data.After importing service file it worked fine.

Answer 3

I was also facing the same issue when i was calling a method inside switchMap, apparently I found that if we use method inside switchMap it must return observable.

i used pipe to return observable and map to perform operations inside pipe for an api call which i was doing inside method rather than subscribing to it.

Answer 4

In my case I mistakely imported Action into my combineEpics, rather than Epic...

Verify all the functions within combine Epics are epic funcitons

Answer 5

In regard to the "You provided an invalid object where a stream was expected. You can provide an Observable, Promise, Array, or Iterable" error.

This could happen if you import { Observable } from 'rxjs' after (below) some module/function/whatever, which actually uses it.

Solution: move this import above the import of that module.

Answer 6

I have the same exact error message while I was doing my unit test and throwing observable exception after mocking my services.

I resolved it by passing exact function and format inside Observable.throw.

Actual code which calls the service and subscribe to get data. notice that catch to handle the 400 error.

     this.search(event).catch((e: Response) => {
        if (e.status === 400) {
          console.log(e.json().message);
        } else if (e.url) {
          console.log('HTTP Error: ' + e.status + ' ' + e.statusText,
            'URL: ' + e.url, 'Info: ' + e.json().message));
        }
      }).finally(() => {
        this.loading = false;
      }).subscribe((bData) => {
        this.data = bData;
      });

The code inside the service

  search() {
    return this.someService.getData(request)
       .do((r) => {
          this.someService.defaultHeaders.delete('skipAlert');
          return r;
        })
      .map((r) => {
          return r.businessObjectDataElements.length && r.businessObjectDataElements || null;
        });
  }

Unit Testing

I have mocked the SomeService and returning observable data and its fine as it have all the required methods inside it.

 someServiceApi = fixture.debugElement.injector.get(SomeService);
 spyOn(someServiceApi, 'getData').and.returnValue(Observable.of({}));

The above code is okey but when when I was trying to test the catch/error condition by passing Observable.throw({}) it was showing me the error as it was expecting Response type return from the service.

So below service mocking return was giving me that error.

someServiceApi.getData
  .and.returnValue(Observable.throw(new Response({status: 400, body: [], message: 'not found error'})));

So I Corrected it by replicating the exact expected function in my return object rather passing a Response type value.

someServiceApi.getData
  .and.returnValue(Observable.throw({status: 400, json: () => { return {message: 'not found error'}}, body: []}));
// see `json: () => { return {message: 'not found error'}}` inside return value