连接到 Firebase db 后如何处理用户注销？

Question

我正在使用 Firebase 和 AngularFire2 库构建一个 Angular2 应用程序。

在建立授权连接后用户注销时如何处理？例如，具有有效帐户的用户登录，连接到我的 Firebase 数据库的“订单”节点，然后用户注销。

我在控制台中收到以下错误，这很有意义。但是我应该如何捕捉这个错误或以其他方式防止它呢？

错误：

FIREBASE WARNING: Exception was thrown by user callback. Error: permission_denied at /orders: Client doesn't have permission to access the desired data.

相关代码（我认为）：

@Injectable()
export class OrderService {

  private orders$: FirebaseListObservable<any>;
  private _pendingOrders$: BehaviorSubject<any> = new BehaviorSubject(null);
  private _activeOrders$: BehaviorSubject<any> = new BehaviorSubject(null);

  constructor(
    private af: AngularFire,
    private auth: AuthService) {
    this.auth.isAuthed
      .subscribe((value: boolean) => {
        if (this.auth.isAuthed.value) {
          const userId = this.auth.getUserId();
          this._subscribeToUserOrders(userId);
        } else {
          // Somehow unsubscribe here, perhaps?
        }
      });
  }

  _subscribeToUserOrders(userId) {
    const query = {
      orderByChild: 'userId',
      equalTo: userId
    };

    this.orders$ = this.af.database
      .list(`orders`, query);

    this.orders$.subscribe((orders) => {
      // Load pending orders
      this._pendingOrders$.next(orders.filter(o => o.status === 'PENDING'));

      // Load active orders
      this._activeOrders$.next(orders.filter(o => o.status === 'ACTIVE'));
    });
  }

  get pendingOrders() {
    return this._pendingOrders$.asObservable();
  }

  get activeOrders() {
    return this._activeOrders$.asObservable();
  }
}

Answer 1

对this.orders$.subscribe 的调用将返回一个RxJS Subscription：

import { Subscription } from 'rxjs/Subscription';

private ordersSubscription: Subscription;
...
this.ordersSubscription = this.orders$.subscribe(...);

你可以用它来取消订阅（你可能也想从你的主题中发出null）：

if (this.auth.isAuthed.value) {
  const userId = this.auth.getUserId();
  this._subscribeToUserOrders(userId);
} else {
  this._unsubscribeFromUserOrders();
}
...
_unsubscribeFromUserOrders() {
  this.ordersSubscription.unsubscribe();
  this.orders$ = null;
  this._pendingOrders$.next(null);
  this._activeOrders$.next(null);
}