无法从 angular2 服务获取结果数组

Question

这是我获取结果数组的服务代码：

  getIndustries(): Observable<any> {
    return this.http.get(`${IndustriesService.BASE_URI}/?searchTerm=`)
                    .map((res: Response) => res.json())
                    .catch((err: any) => Observable.throw('Server Error'));
  }

下面是我的组件构造函数和与上面定义的服务通信的方法。

  protected searchData: Array<Industry>;
  constructor( private completerService: CompleterService,
               private route: ActivatedRoute,
               private industriesService: IndustriesService) { 
      this.fetchIndustryCodes();
    }

  private fetchIndustryCodes(): Subscription {
    return this.route.params
      .switchMap((industries: Industry[]) => this.industriesService.getIndustries())
      .subscribe((industries_data: Industry[]) => {
        this.searchData = industries_data
      });
  }

当我尝试在构造函数中打印此 searchData 时，它会打印一个 Subscription 对象。我不确定如何通过上述订阅获取数据。

关于这方面的任何指导都会有很大的帮助！

Answer 1

据我所知，您想在构造函数中使用 searchData，但您不能这样做，因为异步调用需要时间并且构造函数中的代码在 fetchIndustryCodes() 完成之前执行。如果是这种情况，那你为什么不 subscribe 并在构造函数本身中等待呢？

constructor( private completerService: CompleterService,
           private route: ActivatedRoute,
           private industriesService: IndustriesService) { 

            this.fetchIndustryCodes().subscribe(
            (industries_data) => {
                this.searchData = industries_data;
                // whatever you want to do here.
            }, (err) => {console.log("error here")});
}


 private fetchIndustryCodes(): Observable<type> {
    return this._activatedRoute.params
        .switchMap((industries) => this.industriesService.getIndustries())
        .catch((err) => {console.log(err); return "service error";})
}

无法从 angular2 服务获取结果数组

Not able to fetch an array of results from angular2 service

angular2-services