Question

我写了一个HttpInterceptor，我想在其中使用NotificationService。但是httpInterceptor中的NotificationService未定义。有没有错过。

HttpInterceptor.ts

...<imports>...
export class HttpInterceptor extends Http {


  constructor(
    backend: ConnectionBackend,
    defaultOptions: RequestOptions,
    private notificationService: NotificationService
  ) {
    super(backend, defaultOptions);
  }

  private beforeRequest(): void {
       this.notificationService.showPreloader(); //this.notificationService is undefined
  }
  get(url: string, options?: RequestOptionsArgs): Observable<any> {
    this.beforeRequest();
    return super.get(HttpInterceptor.getFullUrl(url), HttpInterceptor.requestOptions(options))
  }
}

NotificationService.ts

export class NotificationService {
   showPreloader() {
      console.log('preloader show!');
   }
}

AppModule.ts

providers: [ModalModule, NotificationService, {
   provide: HttpInterceptor,
   useFactory: httpFactory,
   deps: [XHRBackend, RequestOptions]
}],
export function httpFactory(backend: XHRBackend, defaultOptions: RequestOptions, notificationService: NotificationService) {
  return new HttpInterceptor(backend, defaultOptions, notificationService);
}

Answer 1

你错过了工厂的一个依赖：

deps: [XHRBackend, RequestOptions, NotificationService]
                                    ^^^^^^^^^^^^^^^^^^
                                       add this

Angular 2：自定义服务在另一项服务中是不可取的

1 个答案: