未处理的异常:无效参数：“CartItemModel”实例

Question

我正在处理一个商店应用程序，在用户下订单后，我想将该订单详细信息存储在防火墙中。在按下按钮后执行该调用的功能如下

 addOrderDetails() {
final user  = Provider.of<UserProvider>(context, listen: false);
writeOrderDetailsForUser({
  "userId" : user.user.uid,
  "description" : "Cash on delivery",
  "status" : "pending",
  "createdAt": DateTime.now().millisecondsSinceEpoch.toString(),
  "totalPrice" : user.userModel.totalCartPrice,
   "cart" : user.userModel.cart,
  "address" : widget.addressId,
  "phone" : user.userModel.phone,
 }).whenComplete(() async {
  for (CartItemModel cartItem in user.userModel.cart){
    bool value = await user.removeFromCart(cartItem: cartItem);
    if(value) {
      user.reloadUserModel();
      ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text("Item has been successfully removed from cart"),));
    }else {
      print(
        "item has not been removed from cart please try again"
      );
    }
  }
  ScaffoldMessenger.of(context).showSnackBar(SnackBar(
    content: Text(
        "Your order has been successfully created, please we will call you in a few minutes to confirm your order"),));
});
changeScreenReplacement(context, NavigationController());

}

Future writeOrderDetailsForUser(Map<String, dynamic> data) async
  {
    await EcommerceApp.firestore
        .collection(EcommerceApp.collectionOrders)
        .document(EcommerceApp.sharedPreferences.getString(EcommerceApp.userUID) + data['createdAt'])
        .setData(data);
  }
}

但是，每当我调用函数时，我都会收到这个错误。

我/颤振(24853)：购物车项目是：‘(package:flutter/src/services/message_codecs.dart:419:7)’E/颤振(24853)的实例:错误:flutter/lib/ui/ui_dart_state.cc(199)未处理异常:无效参数：'CartItemModel' E/颤振(24853)实例：#0 StandardMessageCodec.writeValue StandardMessageCodec.writeValue E/flutter (24853)：#1 FirestoreMessageCodec.writeValue _channel/utils/firestore_message_codec.dart:83:13) E/颤振(24853)：#2 StandardMessageCodec.writeValue (package:flutter/src/services/message_codecs.dart:409:9) E/颤振(24853)：#3 FirestoreMessageCodec.writeValue (package:cloud_firestore_platform_interface/src/method_channel/utils/firestore_message_codec.dart:83:13) E/颤振(24853)：#4 StandardMessageCodec.writeValue。(package:flutter/src/services/message_codecs.dart:416:9) E/颤振(24853)：#5 _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:397:8) E/颤振(24853)：#6 StandardMessageCodec.writeValue (package:flutter/src/services/message_codecs.dart:414:13) E/颤振(24853)：#7 FirestoreMessageCodec.writeValue (package:cloud_firestore_platform_interface/src/method_channel/utils/firestore_message_codec.dart:83:13) E/颤振(24853)：#8 StandardMessageCodec.writeValue。(package:flutter/src/services/message_codecs.dart:416:9) E/颤振(24853)：#9 _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:397:8) E/颤振(24853)：#10 StandardMessageCodec.writeValue (package:flutter/src/services/message_codecs.dart:414:13) E/颤振(24853)：#11 FirestoreMessageCodec.writeValue (package:cloud_firestore_platform_interface/src/method_channel/utilsE/颤振(24853)：#12 (package:flutter/src/services/message_codecs.dart:551:18) E/颤振(24853)：#13 (package:flutter/src/services/platform_channel.dart:150:13) E/颤振(24853)：#14 MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:331:12) E/颤振(24853)：#15 (package:cloud_firestore_platform_interface/src/method_channel/method_channel_document_reference.dart:28:43) E/颤振(24853)：#16 DocumentReference.setData (package:cloud_firestore/src/document_reference.dart:48:22) E/颤振(24853)：#17 _PaymentPageState.writeOrderDetailsForUser (package:maen/screens/placeOrderPayment.dart:349:10) E/颤振(24853)：#18 _(package:maen/screens/placeOrderPayment.dart:316:5) E/ PaymentPageState.addOrderDetails (24853)：#19 _PaymentPageState.build.(package:maen/screens/placeOrderPayment.dart:297:17)

Answer 1

这个问题是由这条线引起的。

 "cart" : user.userModel.cart,

好像你的user.userModel.cart是CartItemModel的列表，

要克服这一问题，您必须将其序列化，然后添加到数据库中，因为数据库对CartItemModel一无所知，

做这样的事：

"cart" : user.userModel.cart.map((e)=>e.toJson()).toList();

在CartItemModel中定义toJson函数

由于细节较少，我假设CartItemModel有类似于id , name and price的字段

Map toJson() => {
        'id': id,
        'name': name,
        'price' : price
      };

这应该能解决你的问题