RxJs实现了Observable链的刷新操作

Question

尝试使用rxjs链实现刷新或轮询。

ngOnInit() {
    const id$ = this.route.params;

    id$.subscribe((params: Params) =>  {
        this.id = params['id'];
        this.userService.getUser(params['id']).subscribe(this.getUserSubject$));
    }

    this.getUserSubject$
      .flatMap(user =>
        Observable.forkJoin(this.userService.getAddress(user), this.userService.isActive(user),
          (address, isActive) => {
            return _.assign({}, user, address, {isActive: isActive});
          }
        )
      )
      .subscribe(user => {
        this.user = user
      }, err => this.error(err));
}

refresh($event) {
    this.userService.getUser(this.id).subscribe(this.getUserSubject$);
}

在刷新调用时，不会调用getUserSubject $链。 它只在ngOnInit上调用一次。 如何将数据推送到getUserSubject $，以便更新用户。 为什么可观察链不会从刷新中调用。