Flutter中Isar搭配Freezed使用时build_runner报Unsupported type错误

问题场景 #

在Flutter项目中同时使用Isar数据库和Freezed进行代码生成时，执行flutter pub run build_runner build命令会报错，提示copyWith getter存在不支持的类型，要求用@ignore标注。

错误代码示例 #

import 'package:freezed_annotation/freezed_annotation.dart';
import 'package:isar/isar.dart';

part 'api_response_model.freezed.dart';
part 'api_response_model.g.dart';

@collection
@freezed
class ApiResponseModel with _$ApiResponseModel {
  const ApiResponseModel._();

  factory ApiResponseModel({
    @JsonKey(name: 'data') String? data,
  }) = ResponseModel;

  Id get id => Isar.autoIncrement;

  factory ApiResponseModel.fromJson(Map<String, Object?> json) =>
      _$ApiResponseModelFromJson(json);
}

错误信息 #

Unsupported type. Please annotate the property with @ignore.
package:freezed_isar/api_response_model.freezed.dart:28:51
   ╷
28 │   $ApiResponseModelCopyWith<ApiResponseModel> get copyWith =>
   │                                                   ^^^^^^^^
   ╵

解决方法 #

问题根源是Freezed自动生成的copyWith getter的类型不属于Isar支持的数据库存储类型，需要告诉Isar忽略这个属性。

有两种可行的修复方式：

方式一：修改@collection注解，指定忽略copyWith #

直接在@collection注解中添加ignore参数，明确忽略copyWith属性：

@collection(ignore: {'copyWith'})
@freezed
class ApiResponseModel with _$ApiResponseModel {
  // 类内容保持不变
}

方式二：显式给copyWith添加@ignore注解 #

在类中显式声明copyWith getter并标注@ignore，覆盖Freezed生成的版本：

@collection
@freezed
class ApiResponseModel with _$ApiResponseModel {
  const ApiResponseModel._();

  factory ApiResponseModel({
    @JsonKey(name: 'data') String? data,
  }) = ResponseModel;

  Id get id => Isar.autoIncrement;

  @ignore
  @override
  $ApiResponseModelCopyWith<ApiResponseModel> get copyWith => super.copyWith;

  factory ApiResponseModel.fromJson(Map<String, Object?> json) =>
      _$ApiResponseModelFromJson(json);
}

两种方式都能让Isar跳过对copyWith的类型校验，顺利完成代码生成。

内容的提问来源于stack exchange，提问作者Saurabh