如何从 firebase firestore 子集合中获取数据？

Question

实际上我想从 firebase 子集合中获取数据。

我想将子集合的数据提取到模型中。

实际上问题是它检索了超级集合的数据，但在子集合中却没有数据。

这是我的第一个模型

class Order{
  Stream<List<OrderedFoodItem>> orderedFoodItemList;      <--- Here OrderedFoodItem is Second Model
  String name;

  Order({this.orderedFoodItemList, this.name});
}

这是我的第二个模型

class OrderedFoodItem{
  String foodItemName;
  String foodItemPrice;
  String foodItemQuantity;

  OrderedFoodItem({this.foodItemName, this.foodItemPrice, this.foodItemQuantity});
}

第一个模型是外部模型，第二个模型是内部模型

这是我的代码，

Stream<List<Order>> get getPendingOrdersList  {
    String collectionPath = uid + "pendingorders";
    final CollectionReference collectionReference = FirebaseFirestore.instance.collection(collectionPath);
    return collectionReference.snapshots().map(_orderList);
  }

  List<Order> _orderList(QuerySnapshot querySnapshot)  {
    return querySnapshot.docs.map((document){
      return Order(
        name: document.get('name'),
        orderedFoodItemList: FirebaseFirestore.instance
            .collection(uid + "pendingorders")
            .doc(document.id).collection(document.id).snapshots().map(_orderedFoodItemList),
      );
    }).toList();
  }

  List<OrderedFoodItem> _orderedFoodItemList(QuerySnapshot querySnapshot) {
    return querySnapshot.docs.map((document) {
      return OrderedFoodItem(
        foodItemName: document.get('fooditem_name'),
        foodItemPrice: document.get('fooditem_price'),
        foodItemQuantity: document.get('fooditem_quantity'),
      );
    }).toList();
  }

我正在获取数据的这段代码

StreamBuilder<List<Order>>(
        stream: DatabaseService(uid: FirebaseAuth.instance.currentUser.uid).getPendingOrdersList,
        builder: (context, snapshot){
          if(snapshot.data != null){
            return ListView.builder(
              itemCount: snapshot.data.length,
              itemBuilder: (context, outerIndex){
                return Column(
                  children: [
                    Text(
                      snapshot.data[outerIndex].name,
                    ),
                    StreamBuilder<List<OrderedFoodItem>>(
                      stream: snapshot.data[outerIndex].orderedFoodItemList,
                      builder: (context,innerSnapshot){
                        if(innerSnapshot.data != null){
                          return ListView.builder(
                            itemCount: innerSnapshot.data.length,
                            itemBuilder: (context, innerIndex) {
                              return Column(
                                children: [
                                  Text(
                                    innerSnapshot.data[innerIndex].foodItemName
                                  ),
                                  Text(
                                      innerSnapshot.data[innerIndex].foodItemPrice
                                  ),
                                  Text(
                                      innerSnapshot.data[innerIndex].foodItemQuantity
                                  ),
                                ],
                              );
                            },
                          );
                        } else {
                          return CircularProgressIndicator();
                        }
                      },
                    ),
                  ],
                );
              },
            );
          }else{
            return Text('no data');
          }

        },
      ),