我如何订阅 Observable 并在 Javascript 对象中使用该值？

Question

总的来说，我对 Observables、RxJS 和 Angular 还很陌生。我正在使用 Angular 7 (Ionic 4)，我很难想出以下问题的解决方案。

在我的应用程序中，我发出如下 HTTP GET 请求：

myData = this.http.get("https://example.com/api").pipe(
  map(results => {
    return results["payload"]
  })
)

这个 HTTP GET 请求 returns 一个具有以下数据的 Observable myData：

const data = [
  {
    "id": 1,
    "name": "abc",
    "description": "test1" 
  },
  {
    "id": 2,
    "name": "def",
    "description": "test2" 
  },

  ...

  ...

]

我想向这个数组中的每个对象添加另一个键 color，如下所示：

const data = [
  {
    "id": 1,
    "name": "abc",
    "description": "test1",
    "color": "green"
  },
  {
    "id": 2,
    "name": "def",
    "description": "test2",
    "color": "red"
  },

  ...

  ...

]

我不想为每个对象硬编码 color 的值，而是想从另一个名为 colorService 的服务中的函数 getColor(id) 中检索此键值。

问题是 colorService.getColor(id) returns 一个 Observable。

问题：如何为数组中的每个对象订阅 colorService.getColor(id)？

我想做这样的事情：

const data = [
  {
    "id": 1,
    "name": "abc",
    "description": "test1",
    "color": <subscribe to colorService.getColor(1)>
  },
  {
    "id": 2,
    "name": "def",
    "description": "test2",
    "color": <subscribe to colorService.getColor(2)>
  },

  ...

  ...

}

希望我说清楚了。我的概念在这一点上相当薄弱，所以如果其中一些听起来令人困惑，我深表歉意。

Answer 1

这就是你能做的[见代码注释中的解释]-

myData = this.http.get("https://example.com/api")
                      .pipe(
                              mergeMap(results => {
                                const data = results["payload"];
                                //I am assuming that `data` is the array that you mentioned in your question
                                //Iterate through each of the object in the array and map it to an observable which
                                //will fetch the color and then return the data with color

                                //obs will be an array of observables for each data
                                const obs = data.map(d => {                                  
                                  return this.colorService.getColor(d.id)
                                             .pipe(
                                               map(color => {
                                                 return {...d, color};
                                               })
                                             );
                                });

                                //wait for all the obs to be returned;
                                return forkJoin(obs);
                              }),
                              tap(dataArrayWithColor => {
                                //dataArrayWithColor will have an array of object which will have data with color
                                console.log(dataArrayWithColor);
                              })
                          );

希望对您有所帮助。

我如何订阅 Observable 并在 Javascript 对象中使用该值？

How do I subscribe to an Observable and use that value in a Javascript Object?

observable

rxjs

ionic-framework

angular

ionic4