如何从请求返回HttpClient响应主体？

我有一个依赖于API响应的内容的组件。我已经设置了解析器，但是在我的数据准备好之前它仍然会返回。

如何使我的pull_categories()函数等待接收到响应主体然后返回？而不是返回一个空对象，因为它不会等待，甚至在下面的情况下也不会调用它。

服务

private _categories = [];

constructor(private http: HttpClient) { }

pull_categories() {
    this.http.post('https://myapi.com/something', null)
    .subscribe(
        data => {
            this._categories = data['response'];
            return this._categories;
        }
    );
}

component.ts

categories = [];

constructor(private route: ActivatedRoute) { }

ngOnInit() {
    this.route.data.subscribe(
        (data: Data) => {
            this.categories = data.categories;
        }
    );
}

解析器

constructor(private categoriesService: CategoriesService) { }

resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<any> | Promise<any> | any {
    return this.categoriesService.pull_categories();
}

app-routing.module.ts

{
    path: '',
    component: HomeComponent,
    resolve: {categories: CategoriesResolverService}
}