Angular2 (rc.6) JSON对象键没有被访问

Question

我正在开始我的第一个Angular2 (rc.6)项目。我有一个JSON对象被成功地发送到一个组件，但我无法访问模板中它的键值。

服务(摘录):

@Injectable()
export class SongService {
  constructor(private http: Http) { }
  getSong(id: number): Promise<Song> {
    let url = '/maxapirest/v1/maxmusic/song/'+id
    console.log(url)
    return this.http
      .get(url)
      .toPromise()
      .then(function(response) {
          console.log(response.json());
          return response.json();
      } )
  }

组件(摘录):

@Component({ 
  selector: 'my-song-reading',
  templateUrl: STATIC_URL+'song-reading.component.html',
  providers: [ SongService ],
})  
export class SongReadingComponent implements OnInit {
  song: Promise<Song>;
  constructor(
    private songService: SongService,
    private route: ActivatedRoute) { }
  ngOnInit(): void {
    this.route.params.forEach((params: Params) => {
      if (params['id'] !== undefined) {
        let id = +params['id'];
        this.song = this.songService.getSong(id)
      }
    });
  }

~

模板(摘录):

<div *ngIf="song">
    {{ song | async | json }}<br/><br/><br/>
    {{ song.title | async}}
    {{ song.image | async }}
    {{ song.id | async}}
</div>

问题我不能弄清楚的是{{song | json}}正确输出json对象:{"id": 71， "title": "It Don't Mean A Thing"…}并且不会抛出错误。但是其他的var键不会被渲染。

任何想法?

Answer 1

您需要使用.then(...)，然后在那里分配值:

  ngOnInit(): void {
    this.route.params.forEach((params: Params) => {
      if (params['id'] !== undefined) {
        let id = +params['id'];
        this.songService.getSong(id)
        .then(json => {
          this.song = json;
        });
      }
    });
  }