How to use angular service within another service

Actually it is easy!

import { Injectable, Inject } from '@angular/core';

import { LoginService } from '../common/login.service';
@Injectable()
export class PermissionService {

  constructor(@Inject(LoginService) private login_service: LoginService) { }

  hasCategoryDeletePerm(){
    const u = this.login_service.getUser()
    return u.is_staff;
  }
}