使用Angular2 Promise从JSON获取数据

服务：

import { Injectable } from '@angular/core';
import { Headers,Http } from '@angular/http';
import 'rxjs/add/operator/toPromise';
import { Hero } from './hero';

private heroesUrl = 'app/heroes';  // URL to web api

constructor(private http: Http) { }

getHeroes(): Promise<Hero[]> {
    return this.http.get(this.heroesUrl)
        .toPromise()
        .then(response => response.json().data as Hero[])
        .catch(this.handleError);
}

零件：

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

@Component({
  selector: 'my-app',template: // some template,styles: // some style,providers: [HeroService]
})

export class AppComponent implements OnInit {
  title = 'Tour of Heroes';
  heroes: Hero[];

  constructor(private heroService: HeroService) { }

  getHeroes(): void {
    this.heroService.getHeroes().then(heroes => {
        this.heroes = heroes;
        console.log('heroes',this.heroes);
    });
  }

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

模型：

export class Hero {
  constructor(
    public id: number,public name: string,public power: string,public alterEgo?: string
  ) {  }
}

我取代了私人英雄Url =’app / heroes’;我的端点是一个JSON文件(private heroesUrl =’app / mockups / heroes.json’;),它包含根据英雄模型的数据.

但是当我运行我的应用程序时,我没有数据,并且有任何错误消息.
我的代码不正确吗？