無法從angular2服務

Question

擷取結果的陣列這是我的服務代碼來獲取結果的數組：

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

下面是我的部件的構造和與上述定義的服務進行通信的方法。

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 
     }); 
    } 

當我試圖把它打印出來searchData在構造它打印認購對象。我不知道如何通過上述訂閱獲取數據。

任何方向對此將是一個很大的幫助！

Answer 1

據我所知，你想在你的構造函數中使用searchData，但是你無法調用異步調用需要時間，並且在fetchIndustryCodes()完成之前構造函數中的代碼纔會執行​​。如果是這樣的話，那你爲什麼不在subscribe並且在構造函數本身中等待呢？

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";}) 
}