toJson 无法正常工作 json 序列化程序未处理的异常：无效的参数：“DietMo​​del”的实例

如何解决toJson 无法正常工作 json 序列化程序未处理的异常：无效的参数：“DietMo​​del”的实例

我正在尝试将数据保存在 firestore 上，但在保存到 toJson 时出错。我创建了两个模型diet-model 和TargetModel 来使用json_serializable: ^4.0.0 和json_annotation: ^4.0.0 存储在firestore 上。 TargetModel 有饮食模型列表。错误是运行时错误

错误：

Unhandled Exception: Invalid argument: Instance of 'DietModel'
[        ] E/flutter (23502): #0      convertPlatformException (package:cloud_firestore_platform_interface/src/method_channel/utils/exception.dart:13:5)
[        ] E/flutter (23502): #1      MethodChannelDocumentReference.set (package:cloud_firestore_platform_interface/src/method_channel/method_channel_document_reference.dart:43:13)
[        ] E/flutter (23502): <asynchronous suspension>
[        ] E/flutter (23502): #2      DietPageRepositoryImpl.setTarget (package:dance/services/firestore/firestore-impl/diet-page-repository-impl.dart:31:5)
[        ] E/flutter (23502): <asynchronous suspension>
[        ] E/flutter (23502): #3      DietPageViewModel.setTargetedModel (package:dance/viewmodels/diet-page-view-model/diet-page-view-model.dart:120:5)
[        ] E/flutter (23502): <asynchronous suspension>

---

import 'package:dance/models/diet-model/diet-model.dart';
import 'package:json_annotation/json_annotation.dart';

part 'targeted-model.g.dart';

@JsonSerializable()
class TargetedModel {
  List<DietModel> targetedBreakfast;
  List<DietModel> targetedLunch;
  List<DietModel> targetedSnacks;
  List<DietModel> targetedDinner;

  TargetedModel(this.targetedBreakfast,this.targetedLunch,this.targetedSnacks,this.targetedDinner);

  factory TargetedModel.fromJson(Map<String,dynamic> json) =>
      _$TargetedModelFromJson(json);

  Map<String,dynamic> toJson() => _$TargetedModelToJson(this);
}

---

import 'package:json_annotation/json_annotation.dart';

part 'diet-model.g.dart';

@JsonSerializable()
class DietModel {
  int calories;
  String name;
  int carbs;
  int fat;
  int protein;
  bool selected;
  int quantity;
  String imageUrl;

  DietModel();

  factory DietModel.fromJson(Map<String,dynamic> json) =>
      _$DietModelFromJson(json);

  Map<String,dynamic> toJson() => _$DietModelToJson(this);
}

---

Future<void> setTarget(DateTime date,TargetedModel model) async {
    await _collectionReferenceTD.doc("$date").set(model.toJson()); // getting error here 
  }

解决方法

添加 @JsonSerializable(explicitToJson: true)

这允许嵌套对象被序列化

此外，您可能还想更新 DietMo​​del 构造函数：

  DietModel({this.calories,this.name...