对象内数组订购后未定义

Question

我试图让多个http请求后的元素，但有一个异步问题，我无法解决。发布我的代码：

Get函数在我的服务：

get() { 
return new Observable(project => { 
    this.channelsService.get().subscribe(
    stations => { 
     this._stations = stations; 
     this._stations.forEach((station) => { 
     station.cssClass = this.channelsService.getCss(station.id.split('/').pop()); 
     station.plstation$thumbnails = this.channelsService.getThumbnails(station.id.split('/').pop()); 
     if (station.plstation$callSign !== '') { 
      const watchliveUrl = this.watchLiveApi + station.plstation$callSign + '/?schema=1.0.0'; 
      this.http.get(watchliveUrl).subscribe(data => { 
      const body = data.json(); 
      station.currentListing = body.currentListing; 
      station.nextListing = body.nextListing; 
      project.next(stations); 
      project.complete() 
      }); 
     } 
     }); 

    }, (error) => { 
     this.mapErrorService.mapError(error, 'Listing service (1)'); 
    }); 
}); 

}

的get（）使用和订阅：

constructor(private listingService: ListingService) { 
this.listingService.get().subscribe((stations) => { 
    this.stripDetails.channelList = stations; 
    // stations[6].currentListing Not undefined 
    console.log(stations); 
    // Now is undefined 
    console.log(stations[6].currentListing); 

}); } 

我如何定义站[6] .currentListing ？

Answer 1

您正在将Observable从http.get()转换为Promise，但您绝不会对该Promise做任何事情。因此，虽然stations被定义在你说的地方，但Promise不会完成，所以currentListing属性将是未定义的。

使用Observable或Promise时，您必须始终等待结果。因此，在这种情况下，如果您要使用承诺，则需要将它们汇总在一起，并且不会输出project，直到它们全部完成。

喜欢的东西：

get() { 
return new Observable(project => { 
    this.channelsService.get().subscribe(
    stations => { 
     this._stations = stations; 
     let responses = this._stations.map((station) => { 
     station.cssClass = this.channelsService.getCss(station.id.split('/').pop()); 
     station.plstation$thumbnails = this.channelsService.getThumbnails(station.id.split('/').pop()); 
     if (station.plstation$callSign !== '') { 
      const watchliveUrl = this.watchLiveApi + station.plstation$callSign + '/?schema=1.0.0'; 
      return this.http.get(watchliveUrl).map(data => { 
      const body = data.json(); 
      station.currentListing = body.currentListing; 
      station.nextListing = body.nextListing; 
      }); 
     } 
     }); 
     // Wait for all requests to complete. 
     Rx.Observable.forkJoin(...responses).subscribe(() => { 
      project.next(stations); 
      project.complete() 
     }); 

    }, (error) => { 
     this.mapErrorService.mapError(error, 'Listing service (1)'); 
    }); 
});