Question

我在 Firebase Firestore DB 中有以下数据库结构：

Doc business -> Col delivery_plan -> Doc delivery_plan -> Col delivery_point -> Doc delivery_point（见{{3 }})

我需要的是从 delivery_plan 集合（基于查询）中获取文档子集及其子集合中的所有文档 delivery_point 和不断变化。

在我的 flutter 应用程序中，我有一个模型类 DeliveryPlanList，我希望每次发生任何变化时都返回它的实例（查询 delivery_plan 或任何 delivery_point 中的任何文档）< /p>

我尝试的是使用 database structure 包组合流，这样我就不需要为每个 delivery_plan 文档打开和关闭 StreamSubscriptions：

  Stream<DeliveryPlanList> deliveryPlanListStream(
    String businessId,
    Set<DeliveryPlanStatus> statuses,
    DateTime date,
  ) {
    return FirebaseFirestore.instance
        .collection('business')
        .doc(businessId)
        .collection('delivery_plan')
        .where('date', isEqualTo: DateFormat('yyyy-MM-dd').format(date))
        .where('status', whereIn: statuses.map((s) => enumToString(s)).toList())
        .snapshots()
        .flatMap((s) {
      var innerStreams = s.docs.map((e) => deliveryPlanStream(businessId, e.data()['id']));
      return CombineLatestStream(innerStreams,
          (List<DeliveryPlan> planList) => DeliveryPlanList(deliveryPlans: planList, lastUpdated: DateTime.now()));
    });
  }

  Stream<DeliveryPlan> deliveryPlanStream(String businessId, String deliveryPlanId) {
    Stream<DocumentSnapshot> planStream = FirebaseFirestore.instance
        .collection('business')
        .doc(businessId)
        .collection('delivery_plan')
        .doc(deliveryPlanId)
        .snapshots();
    Stream<QuerySnapshot> pointsStream = FirebaseFirestore.instance
        .collection('business')
        .doc(businessId)
        .collection('delivery_plan')
        .doc(deliveryPlanId)
        .collection('delivery_point')
        .snapshots();
    return CombineLatestStream.combine2(planStream, pointsStream,
        (planSnapshot, pointsSnapshot) => DeliveryPlan.fromFirebase(planSnapshot, pointsSnapshot));
  }

但是，我并不完全理解 flatMap 的作用，因为当我关闭 deliveryPlanListStream(...) 的订阅时，流似乎从未关闭。当我切换业务、关闭 StreamSubscriptions 并开始一个新的业务时可以看到这一点，其功能与我的 BLoC 中的功能相同：

_deliveryPlansStream?.cancel();
    _deliveryPlansStream =
        GetIt.I<DeliveryRepository>().deliveryPlanListStream(businessId, statuses, date).listen((snapshot) {
      this.add(UpdateDeliveriesEvent(snapshot));
    });

监听这些数据变化的最佳方式是什么？谢谢！

合并 Dart 流 - 使用子集合监听 Firestore 集合的变化

0 个答案: