How to wait until the data from ngrx store is processed?

Question

I'm getting data from ngrx store in component. In the map function, I process the data and prepare it for display in the component. The final result is stored in the object. The component implements filters by query parameters. I subscribe to the activated route to get the current query parameters and then to filter my data. When I'm trying to access proccessed object I recieve empty object instead. How do I get the processed result from ngrx store in subscription to query parameters?

events$: Observable<Event[]>;
eventsByDay = {}; // empty object for proccessed data

ngOnInit(): void {
    this.events$ = this.store.pipe(
      select(EventQuery.getAllEvents),
      filter((events) => events.length > 0),
      map((events: Event[]) => {

      // some logic to proccess data from store

      this.eventsByDay = { //proccessed data };

      return events;
      });
    
    this.activatedRoute.queryParams.subscribe((queryParams) => {
        console.log(this.eventsByDay); --> empty
    });      
}

Answer 1

You can use combineLatest to wait until both observables emit something:

import { combineLatest } from 'rxjs'

...

ngOnInit(): void {
  this.events$ = this.store.pipe(
    select(EventQuery.getAllEvents),
    filter((events) => events.length > 0),
    map((events: Event[]) => {
      // some logic to proccess data from store
      this.eventsByDay = { //proccessed data };
      return events;
    });

  // don't forget to unsubscribe!
  combineLatest([this.activatedRoute.queryParams, this.events$])
    .subscribe(([query, events]) => {
      console.log(events, query);
      console.log(this.eventsByDay); // will be the same as events
    });
}