Angular 2 Tour of Heroes Typescript卡在装载上

我的Angular 2 Tour of Heroes应用程序停留在“正在加载...”并且angular-cli没有报告任何错误，我在教程的第五部分，我不知道问题是什么 . 以下是我认为最重要的文件 . 我希望你能看到问题！编辑：控制台中有一个错误：未捕获的TypeError：无法设置未定义的属性“堆栈”

英雄detail.component.ts

import 'rxjs/add/operator/switchMap';
import { Component, Input, OnInit } from '@angular/core';
import { ActivatedRoute, Params }   from '@angular/router';
import { Location }                 from '@angular/common';

import { Hero } from './hero';
import { HeroService } from './hero.service';

@Component({
  moduleId: module.id,
  selector: 'my-hero-detail',
  templateUrl: 'hero-detail.component.html',
})

export class HeroDetailComponent implements OnInit {
  @Input() hero: Hero;

  constructor(
    private heroService: HeroService,
    private route: ActivatedRoute,
    private location: Location
  ) {

  }

  ngOnInit(): void {
    this.route.params
      .switchMap((params: Params) => this.heroService.getHero(+params['id']))
      .subscribe(hero => this.hero = hero);
  }

  goBack(): void {
    this.location.back();
  }
}

heroes.component.ts

import { Component } from '@angular/core';
import { Hero } from './hero';
import { HeroService } from './hero.service';
import { OnInit } from '@angular/core';

@Component({
  selector: 'my-heroes',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
  template:`
    <h2>My Heroes</h2>
    <ul class="heroes">
      <li *ngFor="let hero of heroes"
        [class.selected]="hero === selectedHero"
        (click)="onSelect(hero)">
        <span class="badge">{{hero.id}}</span> {{hero.name}}
      </li>
    </ul>
    <my-hero-detail [hero]="selectedHero"></my-hero-detail>
  `
})

export class HeroesComponent implements OnInit {
  selectedHero: Hero;
  heroes: Hero[];

  constructor(private heroService: HeroService) {

  }

  onSelect(hero: Hero): void {
    this.selectedHero = hero;
  }

  getHeroes(): void {
    this.heroService.getHeroes().then(heroes => this.heroes = heroes);
  }

  ngOnInit(): void {
    this.getHeroes();
  }
}

app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { HttpModule } from '@angular/http';
import { RouterModule }   from '@angular/router';

import { AppComponent } from './app.component';
import { HeroDetailComponent } from './hero-detail.component';
import { HeroesComponent } from './heroes.component';
import { HeroService } from './hero.service';
import { DashboardComponent } from './dashboard.component';

@NgModule({
  declarations: [
    AppComponent,
    HeroDetailComponent,
    HeroesComponent,
    DashboardComponent
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpModule,
    RouterModule.forRoot([
      {
        path: 'heroes',
        component: HeroesComponent
      },
      {
        path: 'dashboard',
        component: DashboardComponent
      },
      {
        path: '',
        redirectTo: '/dashboard',
        pathMatch: 'full'
      },
      {
        path: 'detail/:id',
        component: HeroDetailComponent
      }
    ])
  ],
  providers: [
    HeroService
  ],
  bootstrap: [AppComponent]
})

export class AppModule {

}

app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'my-app',
  template: `
   <h1>{{title}}</h1>
   <nav>
     <a routerLink="/dashboard">Dashboard</a>
     <a routerLink="/heroes">Heroes</a>
   </nav>
   <a routerLink="/heroes">Heroes</a>
   <router-outlet></router-outlet>
 `
})

export class AppComponent {
  title = 'Tour of Heroes'
}

hero.service.ts

import { Injectable } from '@angular/core';

import { Hero } from './hero';
import { HEROES } from './mock-heroes';

@Injectable()
export class HeroService {
  getHeroes(): Promise<Hero[]> {
    return Promise.resolve(HEROES);
  }

  getHero(id: number): Promise<Hero> {
    return this.getHeroes()
      .then(heroes => heroes.find(hero => hero.id === id));
  }
}

dashboard.component.ts

import { Component, OnInit } from '@angular/core';

import { Hero } from './hero';
import { HeroService } from './hero.service';


@Component({
  moduleId: module.id,
  selector: 'my-dashboard',
  templateUrl: 'dashboard.component.html',
})

export class DashboardComponent implements OnInit {
  heroes: Hero[] = [];

  constructor(private heroService: HeroService) {

  }

  ngOnInit(): void {
    this.heroService.getHeroes()
      .then(heroes => this.heroes = heroes.slice(1, 5));
  }
}