ngrx - chain two store.select slices

Question

In my Todo Cmp I have this code

this.todoListGroup$ = this.ngrx.select(fromRoot.getTodos)
    .flatMap((todos: Todo[]) => {
        console.log(todos)
        this.todos = todos
        this.ngrx.select(fromRoot.getLastChangedTodo);
    })
    .map(lastTodo =>{{
        console.log(lastTodo)
        doSomething(this.todos, lastTodo)
    })

When I subscribe to it I get one more console.log(lastTodo) each time todo changes. I figure that with flatmap and ngrx.select, I'm subscribing to a new Observable each time?

with which operator can I chain two store slices?

EDIT:

As long as the view is in the DOM, I want to stay subscribed to todoListGroup$ since it should keep updating my view.

My solution so far is to define a new slice in the reducer which returns the two desired properties. However, I'm still interested in which operator can effectively chain ngrx single property slices.

Thanks!

Answer 1

This is an approach for RxJs v6+ using the combineLatest operator.

First import the operators and Observable function like this:

import { Observable, combineLatest } from 'rxjs';
import { tap } from 'rxjs/operators';

Then you can use them like this:

combineLatest([
  this.store.pipe(select('users', 'userList')),
  this.store.pipe(select('users', 'accountsList')),
]).pipe(tap(([userList, accountsList]) => console.log(userList, accountsList)))