1. 创建一个名为AuthService的服务，用于存储用户身份验证状态和用户信息。该服务应该有一个名为isAuthenticated的布尔值，以指示用户是否已登录，并有一个名为currentUser的属性，用于存储当前用户的信息。

@Injectable({
  providedIn: 'root'
})
export class AuthService {
  public isAuthenticated: boolean = false;
  public currentUser: User;

  constructor() { }

  login(username: string, password: string) {
    // perform login logic and set isAuthenticated and currentUser properties accordingly
  }

  logout() {
    // perform logout logic and reset isAuthenticated and currentUser properties accordingly
  }
}

2. 在AppComponent中订阅AuthService的isAuthenticated属性，并根据其值更新侧边栏组件。

export class AppComponent implements OnInit {
  public isAuthenticated: boolean = false;

  constructor(private authService: AuthService) {}

  ngOnInit() {
    this.authService.isAuthenticated.subscribe((isAuthenticated: boolean) => {
      this.isAuthenticated = isAuthenticated;
      // call a method to update the sidebar component with the currentUser's information or reset it when the user logs out
    });
  }
}

3. 在侧边栏组件中，订阅AuthService的currentUser属性，并根据其值更新用户信息。

export class SidebarComponent implements OnInit {
  public currentUser: User;

  constructor(private authService: AuthService) {}

  ngOnInit() {
    this.authService.currentUser.subscribe((currentUser: User) => {
      this.currentUser = currentUser;
      // update the sidebar with the currentUser's information
    });
  }
}