从异步第一个 api 调用获取响应（需要时间来获取响应）并将其传递给第二个异步 api 以获得最终响应

Question

第一次和第二次 api 调用都是后调用

someFunction(floor){
floor.entities.forEach(elementId => {
                        let desiredTempForZone;
                        this.getDesiredHeatingTemp(elementId._id).subscribe((des) => 
                                {
                                    desiredTempForZone = des
                                });
                        console.log(desiredTempForZone);
})
}

getDesiredHeatingTemp(eleId){
    //1st api call
    return this.siteService.getScheduleParamsByRoomRef('temp and air and desired and heating', eleId)
    .pipe(
    switchMap(a => {
        console.log(a)
        const obs = a.forEach((m)=>{
          //console.log(m)

        //this is custom function
        let pointId = this.helperService.stripHaystackTypeMapping(m.rows[0]['id']).split(' ')[0];

        //2nd api call
        return this.siteService.getHisPointData(pointId, 'current')
      })
      return forkJoin(obs)
  }))
}

我从第一个 api 调用得到的响应看起来像

a=
cols: (23) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}]
meta: {ver: "2.0"}
rows: [{…}]

a=
 cols: (23) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}]
 meta: {ver: "2.0"}
 rows: Array(1)
      0:
       air: "m:"
       desired: "m:"
       id: "r:5d906-9600-desire"
       kind: "Number"
       __proto__: Object
       length: 1
       __proto__: Array(0)

//第二次api调用

  return this.siteService.getHisPointData(pointId, 'current').subscribe(e => console.log(e))

问题
我也能够从第二个 api 调用中获得响应，但只有当我订阅（如上所述）到 (getHisPointData) api 而我想将此响应传递给 obs 时反过来被传递给下面的调用函数

this.getDesiredHeatingTemp(elementId._id).subscribe((des) => 
                                {
                                    desiredTempForZone = des
                                });

但是 obs 是未定义的

第二次api调用响应

       {meta: {…}, cols: Array(2), rows: Array(1)}
     cols: (2) [{…}, {…}]
     meta: {ver: "2.0", id: "r:5d8df1fc3942df083a4539d5", hisStart: "n:0.0", hisEnd: "n:0.0"}
     rows: Array(1)
        0:
          ts: "t:2019-09-30T13:40:58.761Z UTC"
          val: "n:65"
          __proto__: Object
          length: 1
        __proto__: Array(0)
    __proto__: Object
   {meta: {…}, cols: Array(2), rows: Array(1)}
     cols: (2) [{…}, {…}]
     meta: {ver: "2.0", id: "r:5d8df1fc3942df083a4539d5", hisStart: "n:0.0", hisEnd: "n:0.0"}
     rows: Array(1)
        0:
          ts: "t:2019-09-30T13:40:58.761Z UTC"
          val: "n:70"
          __proto__: Object
          length: 1
        __proto__: Array(0)
    __proto__: Object
           {meta: {…}, cols: Array(2), rows: Array(1)}
     cols: (2) [{…}, {…}]
     meta: {ver: "2.0", id: "r:5d8df1fc3942df083a4539d5", hisStart: "n:0.0", hisEnd: "n:0.0"}
     rows: Array(1)
        0:
          ts: "t:2019-09-30T13:40:58.761Z UTC"
          val: "n:90"
          __proto__: Object
          length: 1
        __proto__: Array(0)
    __proto__: Object

我获得最终价值的旧实现

 this.siteService.getScheduleParamsByRoomRef('temp and air and desired and heating', eleId).subscribe(({ rows }) => {
       if (rows.length > 0) {
           rows.forEach((row) => {
               let pointId = this.helperService.stripHaystackTypeMapping(row['id']).split(' ')[0];

               this.siteService.getHisPointData(pointId, 'current').subscribe(({ rows }) => {
                   if (rows.length > 0) {
                       let HeatingDesired = this.helperService.stripHaystackTypeMapping(rows[0].val);

                   }
               });
           });

       }

   });

Answer 1

你可以这样试试，

someFunction(floor){
floor.entities.forEach(elementId => {
  let desiredTempForZone;
   this.getDesiredHeatingTemp(elementId._id).subscribe((des) => 
   {
     desiredTempForZone = des
   });
 })
}

getDesiredHeatingTemp(eleId){
    //1st api call
    return this.siteService.getScheduleParamsByRoomRef('temp and air and desired and 
      heating', eleId)
    .pipe(
    switchMap(a => {
        let secondApiCallUrlList = [];
        const obs = a.rows.forEach((m)=>{
          //this is custom function
          let pointId = this.helperService.stripHaystackTypeMapping(m.rows[0] 
            ['id']).split(' ')[0]; // here we dont need to create the asynchronisation block because as you said before older implemention is working as expected 

        //2nd api call
       secondApiCallUrlList.push(this.siteService.getHisPointData(pointId, 'current'));
      })
      return forkJoin(secondApiCallUrlList); // so here we are passing the whole array so while you subscribe you will get all response once all api call finished 
  }))
}

如果它没有醒来，请告诉我:)

Answer 2

第一个问题，这里：

const obs = a.forEach((m)=> {

那将是 undefined，因为 undefined 是 forEach 返回的唯一内容。您需要改用map

const obs = a.map((m) => {

和 forkJoin 返回的 observables：

return forkJoin(...obs)

someFunction 的模式相同：map 将数组转换为 observables 数组（不要在映射函数中订阅，返回 observables，而不是订阅），forkJoin创建 observables 数组，最后订阅并消费结果。