如何在switchLayer中触发switchMap？

Question

I have the following code and it is not firing the switchMap. Not sure what im doing wrong.

import { switchMap} from "rxjs/operators";
import { combineLatest } from 'rxjs';

this.companies$ = combineLatest(this.authService.user$, this.filter$ ).pipe(
            switchMap(([user, filter]) =>{
                return this.afs.collection<CompanyProfile>('companies', ref => {
                console.log("this doesnt fire"); 
                if (user) { ref.where('owner.network', '==', user.activeNetworkProfile.id) };
                if (filter) { ref.where('name', '==', filter) };
                return ref;
                }).valueChanges();
            } 
        ));

Answer 1

The reason the switchMap never fired was because the filter$ observable was never initialized. I added the following code to the constructor and it worked.

this.filter$ = new BehaviorSubject(null);