angular 2 Observable完全没有调用

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);
    }

}

问题是,如果我理解正确,订阅需要三个回调参数.subscribe(success,failure,complete);.但就我而言,完整的部分永远不会被执行.我想这与switchMap的工作原理有关.我对吗？