Question

我是rxjs的新手，使用forkJoin时遇到问题。

我有一个角度服务，向其他两个角度服务询问数据并将返回的组合数据返回给组件。

但是当我在我的角度组件中使用以下代码片段调用该服务时，我没有得到所有数据：

this.timeseriesKpiData = this.timeseriesKpiDataService
      .getLatestTimeseriesKpi(this.assetId, this.aspectName, this.variableName,

这是我在服务中调用的方法：

timeseriesKpiDataService.ts：

 public getLatestTimeseriesKpi(
    assetId: string,
    aspectName: string,
    variableName: string
  ): any {

    const timeseriesKpiData = {
      name: '',
      value: 'no value found',
      unit: '',
      properties: [
        {
          name: 'Asset',
          value: 'Unknown Asset'
        }
      ]
    };

    // set variableName and aspectName
    timeseriesKpiData.name = variableName;
    timeseriesKpiData.properties.concat( {
      name: 'Aspect',
      value: aspectName} );

    forkJoin (
      // get latest timeseries from another service
      this.timeseriesService.getLatestTimeseriesValue(assetId, aspectName)
        .pipe(
          map((latestTimeseries: Timeseries) => {
            return latestTimeseries;
          }
        )),

      // get unit
      this.aspectService.getUnit(assetId, aspectName)
        .pipe(
          map((unit: any) => {
            return unit;
          })
      )).subscribe(([latestTimeseries, unit]) => {
        if (latestTimeseries !== undefined) {

          // set value
          timeseriesKpiData.value = latestTimeseries[timeseriesKpiData.name];

          // set unit
          timeseriesKpiData.unit = unit;
       }
      }
      });  // end of forkjoin

      return timeseriesKpiData; // how to return it?
    }

我认为问题出在forkjoin上，当我将数据返回到组件时它仍在运行，因此我没有获得所有必需的数据（未设置timeseriesKpiData.value）。

所以我的问题是，如何在我将数据返回到组件之前如何从forkjoin返回数据，或以某种方式等待forkjoin结束？

Answer 1

您应该返回forkjoin，以便您的代码看起来像

public getLatestTimeseriesKpi(
    assetId: string,
    aspectName: string,
    variableName: string
  ): any {

    const timeseriesKpiData = {
      name: '',
      value: 'no value found',
      unit: '',
      properties: [
        {
          name: 'Asset',
          value: 'Unknown Asset'
        }
      ]
    };

    // set variableName and aspectName
    timeseriesKpiData.name = variableName;
    timeseriesKpiData.properties.concat( {
      name: 'Aspect',
      value: aspectName} );

   return forkJoin (
      // get latest timeseries from another service
      this.timeseriesService.getLatestTimeseriesValue(assetId, aspectName),

      // get unit
      this.aspectService.getUnit(assetId, aspectName));  // end of forkjoin
    }

然后在您的组件中

this.timeseriesKpiDataService
      .getLatestTimeseriesKpi(this.assetId, this.aspectName, this.variableName).subscribe(([latestTimeseries, unit]) => {
        if (latestTimeseries !== undefined) {
         this.timeseriesKpiData:any ={};
          // set value
          this.timeseriesKpiData.value = latestTimeseries[timeseriesKpiData.name];

          // set unit
          this.timeseriesKpiData.unit = unit;

       }
      }
  })

如何从forkJoin返回数据

1 个答案: