根据先前响应的结果顺序级联 Observables 并重新映射到新的数据对象 [英] Sequential cascade Observables according result from previous response and remap to new data object

问题描述

我在使用 Observables 即 RxJs 6 的强大功能时遇到困难来正确地pipe、tap、map、mergemap 或任何我的 HttpClient 请求.具有所有不同功能的版本地狱使它不是很容易......

I have difficulties using the power of Observables i.e. RxJs 6 to correctly pipe, tap, map, mergemap or whatever my HttpClient requests. The version hell with all the different functions makes it not very easy...

所以我需要首先进行 REST 调用，然后根据结果可能进行第二次 REST 调用并将可能收到的两个数据对象映射到一个新数据对象中.该函数应该返回一个 Observable.

So what I need is to first make a REST call, then depending on the result probably do a second REST call and map the potentially two received data objects in one new data object. The function should return an Observable.

所以目前，我使用 subject 解决了这个问题，我可以手动/按顺序完成我需要的操作.在这种情况下，该函数返回一个 Subject，而不是 Observable.但是由于调用者只是订阅了这个函数，所以它可以工作.值得一提的是，下面的两个服务函数(userService.loadUserDetails() 和 adminService.getAdminData())只返回它们从 HttpClient 获得的可观察值.

So currently, I solved it with a subject that I am be able to do manually / sequentially what I need. The function returns a Subject, not an Observable in this case. But since the caller just subscribes to this function, it works. To mention is that the two service functions below (userService.loadUserDetails() and adminService.getAdminData()) just returns observables they get from HttpClient.

那么谁能帮我将下面的示例代码翻译成典型的 RxJs 6 代码?

So can anybody help me translate this example code below into typically RxJs 6 code?

myFunction(): Observable<any> {
   const s = new Subject();
    let obj: any = {};

    this.userService.loadUserDetails().subscribe((userDetails) => {
        obj.user = userDetails;
        if (userDetails.authorities.includes('ADMIN')) {
            this.adminService.getAdminData().subscribe((adminData) => {
                obj.adminData = adminData;
                s.next(obj);
                s.complete();
            });
        } else {
            s.next(obj);
            s.complete();
        }
    });

    return s;
}

推荐答案

使用 mergeMap 链接并有条件地返回

Use mergeMap to chain and return conditionally

更新:将mergeMap更改为switchMap Incase内部observable是一个连续的流，当源observable发出时它也会取消内部observable.

Update: changed mergeMap to switchMap Incase inner observable is a continuous stream and when source observable emit it will also cancel the inner observable .

    this.userService.loadUserDetails().pipe(
    switchMap(user=>
      user.authorities.includes('ADMIN')) ?
      this.adminService.getAdminData().map(adminData=>({adminData,user})):
      Observable.of({user}))
      )
    .subscribe();

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