类型“Observable<Observable<Response>>”不能赋值给类型“Observable<Response>”

Question

使用Angular 10，我有以下方法：

private getUser() : Observable<Response> {

  return this.authenticationService.getClaims('sub').pipe(map((claims: Claim[]) => {

    let request: Request = { userId: 1 };

    return this.userService.getByUserId(request).pipe(
      map((payload: Payload<Response[]>) => payload.result[0])
    );

  }));

}

我得到了一个错误：

Type 'Observable<Observable<Response>>' is not assignable to type 'Observable<Response>'.

如何解决这个问题？

Answer 1

创建内部可观察对象需要展平，这可以使用SwitchMap/MergeMap运算符实现，如下所示：

private getUser() : Observable < Response > {

  return this.authenticationService.getClaims('sub').pipe(
    switchMap((claims: Claim[]) => {

      let request: Request = { userId: 1 };

      return this.userService.getByUserId(request).pipe(
        map((payload: Payload<Response[]>) => payload.result[0])
      );

    }));

}

这里有一篇关于Understanding RxJS map, mergeMap, switchMap and concatMap的很棒的文章