Flutter：按日期讀取和合並 firestore 數據

Question

我正在尋找一種方法來按日期合並我從 Cloud Firestore 讀取的數據。 我的目標是從 Cloud Firestore 讀取所有文檔，然后將特定日期的所有文檔放在 ONE ExpansionTile下。 即每個日期一個ExpansionTile ，每個ExpansionTile可能包含許多單獨的文檔，具體取決於當天上傳的文檔數量。

我在從 Cloud Firestore 讀取數據時沒有問題，但是一旦掌握了手頭的信息，我就很難弄清楚如何按日期組織和合並文檔。 請記住，會有多個不同的日期，每個日期都有不同數量的文件。

如下圖所示，我目前有三個具有相同日期的文檔，因此在應用程序中創建它們時有三個不同的ExpansionTiles 。 我希望將這三個轉換為一個ExpansionTile

我目前正在使用flutter_bloc package 按日期從 Cloud Firestore 讀取數據：

    //Retrieves firebase data of all orders done in the past
  Stream<OrderHistoryState> _loadOrderHistory() async* {
    try {
      _orderSubscription?.cancel();

      var orderHistory = Firestore.instance
          .collection('orders')
          .orderBy('date', descending: true);

      _orderSubscription = orderHistory.snapshots().listen(
        (event) {
          if (event.documents.length > 0) {
            add(OrderHistoryUpdate(
              documents: event.documents,
            ));
          } else {
            print("No Order to Load");
            add(NoOrderHistory());
          }
        },
      );
    } catch (e) {
      print("Error with Tracking Status, $e");
          add(ErrorOrderHistory());
        }  
}

Answer 1

對於那些可能好奇的人，這是我對問題的解決方案。 它可能有點冗長，所以任何縮短/改進它的建議仍然非常感謝：

                  //Make sure that there are documents within firebase
                  if (state.orderHistoryDocuments.length != 0) {
                    //Adding the first document manually so that
                    //the forloop section has something to compare dates
                    //This listForEachDate is for storing a collection
                    //of all documents of one date
                    listForEachDate = [state.orderHistoryDocuments[0].data];
                    //listOfDateLists is a list of all listForEachDate
                    //This gives us a list of lists with the documents
                    //separated by date i.e.
                    //[[date1, date1], [date2], [date3, date3, date3], etc]
                    listOfDateLists = [];

                    //i = 1 because index 0 already added above
                    for (int i = 1;
                        i < state.orderHistoryDocuments.length;
                        i++) {
                      //If the current index's date matches that of the previous
                      //index's date, then add it to the listForEachDate
                      if (state.orderHistoryDocuments[i]
                              .data["dateCreated"] ==
                          state.orderHistoryDocuments[i - 1]
                              .data["dateCreated"]) {
                        listForEachDate
                            .add(state.orderHistoryDocuments[i].data);
                        //If [index]date does not match [index - 1]date
                        //Then add the current listForEachDate to the
                        //listOfDateLists i.e. add sublist to list of lists
                      } else {
                        listOfDateLists.add(listForEachDate);
                        //Clear the listForEachDate so that we can create
                        //a new clean list of new dates
                        listForEachDate = [];
                        //Add the new date to the listForEachDate
                        //so that the process can start again
                        listForEachDate
                            .add(state.orderHistoryDocuments[i].data);
                      }
                    }
                    //Once the document has been iterated through,
                    //Add to the big list.
                    listOfDateLists.add(listForEachDate);
                  }