HarmonyOS page如何监听数据变化

page如何监听一个单例中的数据变化，page的struct不支持registerDelegate。目前的解决方案是给page一个object成员进行监听，是否有更合适的方案。aboutToAppear注册的监听，理论上是否需要在aboutToDisappear中移除？

export interface LoginDelegate {
  onLogin(): void

  onLogout(): void
}

export class LoginService {
  private static instance: LoginService;
  delegateArray: Array<LoginDelegate> = []

  registerDelegate(delegate: LoginDelegate): void {
    this.delegateArray.push(delegate)
  }

  // 后面是一些业务接口，比如登录、登出
  // 当登录状态发生变化时通过delegate发出
}

class LoginPageAgent implements LoginDelegate {
  @Track status: LoginStatus = LoginStatus.LoggedOut;

  onLogin(): void {
    this.status = LoginStatus.LoggedIn
  }

  onLogout(): void {
    this.status = LoginStatus.LoggedOut
  }
}

@Component
struct LoginPage {
  @State agent: LoginPageAgent = new LoginPageAgent()

  aboutToAppear(): void {
    LoginService.shared().registerDelegate(this.agent)
  }

  build() {
    Column({}) {
      if (this.agent.status == LoginStatus.LoggedIn) {
        Text(`已登录`)
      } else {
        this.loginInput()
      }
    }
  }
}
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