`未处理的异常：无效的参数：'_$_Category'的实例`在将数据发送到firestore时形成一个冻结的生成类

Question

我创建了两个冻结模型类。一个类里面有其他类的参数。当我尝试将数据发送到 Firestore 时，问题就开始了。出现以下错误。

E/flutter ( 6175): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: Invalid argument: Instance of '_$_Category'
E/flutter ( 6175): #0      convertPlatformException
package:cloud_firestore_platform_interface/…/utils/exception.dart:14
E/flutter ( 6175): #1      MethodChannelDocumentReference.set
package:cloud_firestore_platform_interface/…/method_channel/method_channel_document_reference.dart:44
E/flutter ( 6175): <asynchronous suspension>
E/flutter ( 6175): #2      _JsonCollectionReference.add
package:cloud_firestore/src/collection_reference.dart:109
E/flutter ( 6175): <asynchronous suspension>
E/flutter ( 6175): #3      _WithConverterCollectionReference.add
package:cloud_firestore/src/collection_reference.dart:180
E/flutter ( 6175): <asynchronous suspension>
E/flutter ( 6175): #4      _HomeScreenState.product
package:mr_grocery/home/home_screen.dart:45
E/flutter ( 6175): <asynchronous suspension>

模型类

1. 产品（有Category类的参数）

@freezed
class Product with _$Product {
  const factory Product({
    required int amount,
    required List<Category> categories, // Category class generated by freezed
    required String description,
    required List<String> images,
    required bool inStock,
    required String name,
    required String quantity,
    dynamic soldQuantity,
    dynamic createdAt,
    dynamic updatedAt,
    bool? exclusive,
  }) = _Product;

  factory Product.fromJson(Map<String, dynamic> json) =>
      _$ProductFromJson(json);
}

1. 类别

@freezed
class Category with _$Category {
  const factory Category({
    required String image,
    required String name,
    // @_ColorSerlizeable() required Color? color,
  }) = _Category;

  factory Category.fromJson(Map<String, dynamic> json) =>
      _$CategoryFromJson(json);
}

使用 Firestore 包中的 withConverter

  CollectionReference<Product> products() {
    const path = FirebasePaths.products;
    return _firestore.collection(path).withConverter<Product>(
          fromFirestore: (snapshot, options) => Product.fromJson(
            snapshot.data() ?? const {},
          ),
          toFirestore: (value, options) => value.toJson(),
        );
  }

build.yaml

targets:
  $default:
    builders:
      json_serializable:
        options:
          # Options configure how source code is generated for every
          # `@JsonSerializable`-annotated class in the package.
          #
          # The default value for each is listed.
          any_map: false
          checked: false
          constructor: ""
          create_factory: true
          create_to_json: true
          disallow_unrecognized_keys: false
          explicit_to_json: true // -- Specified to true
          field_rename: none
          generic_argument_factories: false
          ignore_unannotated: false
          include_if_null: true

Answer 1

它的行为类似于 explicit_to_json: false，因为它正在尝试对您的类进行编码，而不是使用嵌套的 toJsons。

在您的顶级课程中，它生成的toJson 应该是这样的：

{
  "myNestedClass": myNestedClass.toJson(),
{

而不是

{
  "myNestedClass": myNestedClass,
{

导致此崩溃的原因。

尝试了解您的explicit_to_json: true 为何不起作用。您可以留下更多详细信息，以便我更果断地帮助您。

您是否添加part 'product.g.dart'; 来生成json_serializable 代码？

此外，如果您正在使用 Firebase，请考虑设置 any_map: true，因为 Firebase 结构可能具有 Map<dynamic, dynamic> 而不仅仅是 Map<String, Object?>。