Get nested state slices

One very common tasks when deriving state is selecting a single value out of the whole state. If you are familiar with RxJS, you will know about the pluck operator which "plucks" out values from an object. Also, the map operator could be used for this.

As shown in deriving simple state we use stateful operator from @rx-angular/state to get basic observable handling right out of the box.

import { Observable } from 'rxjs';
import { pluck } from 'rxjs/operators';
import { stateful } from '@rx-angular/state';

const state$: Observable<{ person: { name: string } }>;
const derivation3$ = state$.pipe(stateful(pluck('person', 'name')));

We could even save more code by using the select operator which essentially is a combination of stateful and pluck.

import { Observable } from 'rxjs';
import { select } from '@rx-angular/state';

const state$: Observable<{ person: { name: string } }>;
const derivation4$ = state$.pipe(select('person', 'name'));