Angular 如何将可观察对象映射为内部可观察对象？

如何将可观察对象映射为内部可观察对象

以下是如何获取项目的详细信息。我想用未包装的属性映射接收到的对象

              this.fetchData.getItemData().pipe(
                mergeMap((item: any) => {
                    return {
                        ...item,
                        images: item.images.map(id => this.http.get(baseUrl + link)) -->> I want to unwrap here. (it is an observable; that's why!)
                    }
                })
              )

在这里，我正在映射内部属性图像，它是一个数组到一个可观测数组

这就是我尝试过的：

              this.fetchData.getItemData().pipe(
                forkJoin((item: any) => {
                    return {
                        ...item,
                        images: item.images.map(id => this.http.get(baseUrl + link)) 
                    }
                })
              )


              this.fetchData.getItemData().pipe(
                mergeMap((item: any) => {
                    return {
                      ...item,
                      images: item.images.map((id) =>
                        flatMap(() => this.http.get(baseUrl + link))
                      ),
                    };
                })
              )

---

尝试此操作，将外部值设置为

itemResponse

，然后稍后使用

import { mergeMap, map } from 'rxjs/operators';
....
let itemResponse: any;
this.fetchData.getItemData().pipe(
  mergeMap((item: any) => {
    // assign itemResponse to item be used later
    itemResponse = item;
    // switch to all images
    return forkJoin(...item.images.map((id) => this.http.get(baseUrl + link)));
  }),
  // spread itemResponse and assign images property to images value and return the object
  map(images => ({ ...itemResponse, images })),
);

这是一个例子

由于只有两个级别的请求，您可以简单地嵌套：

this.fetchData.getItemData().pipe(
  mergeMap((item: any) => forkJoin(item.images.map(id => this.http.get(baseUrl + link))).pipe(
    // At this point all previous results are in scope so format the result as required
    map(images => ({...item, images})
  )
);

如果您不喜欢嵌套，或者对于更通用的解决方案，可以使用实用程序操作符（注意，我参与了它的实现）：

// fetch all the data, with all results aggregated into an object
concatJoin(
  {item: this.fetchData.getItemData()},
  {images: ({item:any}) => forkJoin(item.images.map(id => this.http.get(baseUrl + link)))}  
).pipe(
  // convert it into the format you want
  map(({item:any, images}) => ({...item, images}))
);