angular 2 Observable complete not called

Question

I am playing around with hero app fro angular 2 tutorial and right now i have this Component

import { Component, OnInit } from '@angular/core'
import { Subject } from 'rxjs/Subject';
import { Hero } from "./hero";
import { Router } from "@angular/router";
import { HeroService } from "./hero.service";
import { BehaviorSubject } from "rxjs/BehaviorSubject";


@Component({
    selector: 'hero-search',
    templateUrl: 'app/hero-search.component.html',
    styleUrls: ['app/hero-search.component.css'],
})
export class HeroSearchComponent implements OnInit{
    heroes: Hero[];
    isLoading: BehaviorSubject<boolean> = new BehaviorSubject(false);
    error: any;
    private searchNameStream = new Subject<string>();

    constructor(
        private heroService: HeroService,
        private router: Router
    ) {}

    ngOnInit() {
        this.searchNameStream
            .debounceTime(400)
            .distinctUntilChanged()
            .switchMap(name => {
                this.isLoading.next(true);
                return this.heroService.getHeroesByName(name)
            })
            .subscribe(
                heroes => this.heroes = heroes,
                error => this.error = error,
                () => {
                    console.log('completed');
                    this.isLoading.next(false);
                })
    }

    // Push a search term into the observable stream.
    search(Name: string): void {
        this.searchNameStream.next(Name)
    }

    gotoDetail(hero: Hero): void {
        let link = ['/detail', hero.id];
        this.router.navigate(link);
    }

}

The problem is that, if i understand it correctly, subscribe takes three callback parameters .subscribe(success, failure, complete); . But in my case the complete part is never executed. I guess it has something to do with how switchMap works. Am i right?

Answer 1

The searchNameStream never completes, so the observable obtained from switchMap never completes either.

Every time an event is emitted by the searchNameStream , heroService.getHeroesByName() is called and all the events emitted by this "inner" observable are reemitted by the "outer" observable, until a new event is emitted by the searchNameStream , and this process repeats. You subscribed to the outer observable, which will only complete when the searchNameStream completes.