Как извлечь пользовательский объект из Firestore?

Question

Я не могу извлечь объекты MenuItem, называемые line_items, из Firestore.Вот консоль, показывающая, что есть у Firebase:

document.data() is ["status": PENDING, "account_id": 
0EE2S7CZeLVMbJ5fujwgKqUHGp53, "total_amount": 544, 
"balance_amount": 544, "date": 1553540151000, "discount_amount": 0, 
"notes": , "tip_amount": 0, "reward_amount": 0, "balance_id": 
QaC1hQwgAHHlCP0rAvgR, "subtotal": 500, "line_items": <__NSArrayM 
0x6000029184e0>(
{
basePrice = 100;
category = Beans;
description = "La Colombe 2.2 Kg Bag";
itemId = RWQ7QDTACJRTLHGXX3WNUQHE;
modifierKeys =     (
    NNZVHCFWVUT5DDQMJ5BOYHXS,
    VXVVAAVTLFVPCA66EGTWHBTX
);
name = "La Colombe 2.2Kg BAG";
photoUrl = "https://square-production.s3.amazonaws.com/files/d13f686c4b8995914642f9ddd61491182e9bcd7f/original.jpeg";
quantity = 2;
size = Regular;
sizeAddOnPrice = 150;
toppingsAddOnPrice = 0;
totalModPrice = 150;
totalPrice = 250;
unitPrice = 250;
}
), "tax_amount": 44, "location_id": 0M8QD6ZY890RT]

Вот функции, отвечающие за получение данных транзакции.Первые две работы.Третий нет.Он возвращает line_items как пустой словарь, когда он должен иметь значения.

public func getTransactionData(completion: @escaping (([Order]?) -> ())) {
    guard let userId = Auth.auth().currentUser?.uid else { completion(nil); return }
    let db = Firestore.firestore()
    let query = db.collection("order").whereField("account_id", 
isEqualTo: userId)
    query.getDocuments() { (querySnapshot, err) in
        if let err = err {
            print("Error getting documents: \(err)")
        } else {
            guard let querySnapshot = querySnapshot else { 
 completion(nil); return }
            var orders = [Order]()
            for document in querySnapshot.documents {
                let order = self.extractOrder(document)
                if let order = order {
                    orders.append(order)
                }
                }
                completion(orders)
            }
        }
    }

private func extractOrder(_ document: QueryDocumentSnapshot) -> Order? {
    print("document.data() is \(document.data())")
    let lineItems = extractLineItems(document.data()["line_items"] as? [[String:Any]] ?? [[:]])
        let orderId = document.documentID
    guard let balanceId = document.data()["balance_id"] as? String,
        let accountId = document.data()["account_id"] as? String,
        let subtotal = document.data()["subtotal"] as? Int,
        let date = document.data()["date"] as? Int,
        let totalAmount = document.data()["total_amount"] as? Int,
        let notes = document.data()["notes"] as? String,
        let rewardAmount = document.data()["reward_amount"] as? Int,
        let status = document.data()["status"] as? String,
        let tax = document.data()["tax_amount"] as? Int,
        let tip = document.data()["tip_amount"] as? Int,
        let balanceAmount = document.data()["balance_amount"] as? Int,
        let discountAmount = document.data()["discount_amount"] as? Int,
        let locationId = document.data()["location_id"] as? String
        else { return nil }
    let order = Order(totalAmount: totalAmount, subtotal: subtotal, discountAmount: discountAmount, tipAmount: tip, taxAmount: tax, balanceAmount: balanceAmount, rewardAmount: rewardAmount, balanceId: balanceId, accountId: accountId, locationId: locationId, date: date, status: status, orderType: "PICK UP", lineItems: lineItems, notes: notes, orderId: orderId)
    print("order is \(order)")
    return order
}

var modifiers: [Modifier]?
var toppings: [String]?

private func extractLineItems(_ dictionaryArray: [[String:Any]]) -> [MenuItem] {
    var lineItems = [MenuItem]()
    let count = dictionaryArray.count
    for x in 0..<count {
        guard let itemId = dictionaryArray[x]["item_id"] as? String,
            let category = dictionaryArray[x]["category"] as? String,
            let name = dictionaryArray[x]["name"] as? String,
            let description = dictionaryArray[x]["description"] as? String,
            let photoUrl = dictionaryArray[x]["photoUrl"] as? String,
            let basePrice = dictionaryArray[x]["base_item_price"] as? Int,
            let unitPrice = dictionaryArray[x]["unit_price"] as? Int,
            let totalPrice = dictionaryArray[x]["total_price"] as? Int,
            let quantity = dictionaryArray[x]["quantity"] as? Int,
            let size = dictionaryArray[x]["size"] as? String,
            let modifierKeys = dictionaryArray[x]["modifierKeys"] as? [String],
            let sizeAddOnPrice = dictionaryArray[x]["sizeAddOnPrice"] as? Int,
            let toppingsAddOnPrice = dictionaryArray[x]["toppingsAddOnPrice"] as? Int
            else { continue }
        if let modifiers = dictionaryArray[x]["modifiers"] as? [Modifier] {
            self.modifiers = modifiers
        } else {
            self.modifiers = nil
        }
        if let toppings = dictionaryArray[x]["toppings"] as? [String] {
            self.toppings = toppings
        } else {
            self.toppings = [String]()
        }
        let totalModPrice = sizeAddOnPrice + toppingsAddOnPrice
        let lineItem = MenuItem(itemId: itemId, name: name, modifiers: self.modifiers, photoUrl: photoUrl, quantity: quantity, basePrice: basePrice, unitPrice: unitPrice, totalPrice: totalPrice, totalModPrice: totalModPrice, sizeAddOnPrice: sizeAddOnPrice, toppingsAddOnPrice: toppingsAddOnPrice, description: description, size: size, toppings: self.toppings, category: category, modifierKeys: modifierKeys)
        lineItems.append(lineItem)
    }
    return lineItems
}