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我收到以下错误，我相信这是因为 null 安全，这意味着没有收到任何数据或 getSignedInUser() 方法不正确或类BuiltValueConverter是原因。

（我用 Postman 测试了令牌并检索了数据）

E/flutter (21792): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] 未处理的异常：未处理的错误 Null 检查运算符用于空值，发生在“AuthBloc”实例中。E/flutter (21792): #0
BuiltValueConverter._deserialize package:todo_list_app/…/auth/built_value_converter.dart:51 E/flutter (21792): #1 BuiltValueConverter._convertToCustomObject package:todo_list_app/…/auth/built_value_converter.dart:36 E/flutter (21792)：#2 BuiltValueConverter.convertResponse 包：todo_list_app/…/auth/built_value_converter.dart:25

我正在使用带有built_value Pubs 的斩波器。我正在尝试将即将到来的 json 转换为对象。例子：

{“用户名”：“杰克”，“电子邮件”：“jack2066@gmail.com”，“用户角色”：“用户”，“created_at”：“2021-07-03T16:49:56.774Z”，“updated_at”： “2021-07-03T16:49:56.774Z”}

错误开始的以下代码也在本教程转换器和内置值集成中进行了说明

import 'package:built_collection/built_collection.dart';
import 'package:chopper/chopper.dart';
import 'package:todo_list_app/infrastructure/remote/auth/models/serializers.dart';

class BuiltValueConverter extends JsonConverter {

  @override
  Request convertRequest(Request request) {
    return super.convertRequest(
      request.copyWith(
        body: serializers.serializeWith(
          serializers.serializerForType(request.body.runtimeType)!,
          request.body,
        ),
      ),
    );
  }

  @override
  Response<BodyType> convertResponse<BodyType, SingleItemType>(
    Response response,
  ) {
    final Response dynamicResponse = super.convertResponse(response);
    final BodyType customBody =
        _convertToCustomObject<SingleItemType>(dynamicResponse.body);//
    return dynamicResponse.copyWith<BodyType>(body: customBody);
  }


  dynamic _convertToCustomObject<SingleItemType>(dynamic element) {
    if (element is SingleItemType) return element;

    if (element is List)
      return _deserializeListOf<SingleItemType>(element);
    else
      return _deserialize<SingleItemType>(element);
  }

  BuiltList<SingleItemType> _deserializeListOf<SingleItemType>(
    List dynamicList,
  ) {
    // Make a BuiltList holding individual custom objects
    return BuiltList<SingleItemType>(
      dynamicList.map((element) => _deserialize<SingleItemType>(element)),
    );
  }

  SingleItemType _deserialize<SingleItemType>(Map<String, dynamic> value,) {
    // We have a type parameter for the BuiltValue type, which should be returned after deserialization.
    return serializers.deserializeWith(
      serializers.serializerForType(SingleItemType)!, // Error Start
      value,
    );
  }

}

这是我的 Chopper 服务代码，getSignedInUser抛出错误。我不知道getSignedInUser方法的实现是否正确。

import 'package:chopper/chopper.dart';
import 'package:injectable/injectable.dart';
import 'package:todo_list_app/infrastructure/remote/auth/built_value_converter.dart';
import 'package:todo_list_app/infrastructure/remote/auth/models/auth_built_model.dart';
import 'package:todo_list_app/infrastructure/remote/core/constants.dart';

part 'auth_service.chopper.dart';

@singleton
@ChopperApi() 
abstract class AuthService extends ChopperService {
  @factoryMethod
  static AuthService create() {
    final client = ChopperClient(
      baseUrl: AUTH_BASE_URL_External,
      services: [
        _$AuthService(),
      ],
      converter: BuiltValueConverter(),
      errorConverter: JsonConverter(),
      interceptors: [
        HttpLoggingInterceptor()
      ],
    );
    return _$AuthService(client);
  }

  @Post(path: '/signup')
  Future<Response> signUp(@Body() RegisterRequestModel body);

  @Post(path: '/signin')
  Future<Response<LoginResponseModel>> singIn(@Body() LoginRequestModel body);

  //headers: {AUTH_HEADER:BEARER+'authValue'}
  @Get(path: '/auth', )//authValue='Bearer Token'
  Future<Response<UserResponseModel>> getSignedInUser(@Header("Authorization") String authValue);//error Unhandled error Null check operator used on a null value
}

知道如何解决此错误吗？还有 Chopper 或具有良好文档的替代 pub 的良好文档吗？谢谢

4

2 回答 2

1

我认为您的“serielizers.dart”文件中缺少值，应如下所示：

    @SerializersFor(const[RegisterRequestModel,LoginRequestModel,UserResponseModel])
final Serializers serializers =
(_$serializers.toBuilder()..addPlugin(StandardJsonPlugin())).build();
于 2021-12-05T12:36:20.190 回答
0

是的，正如你所说，这是因为零安全性。您_deserialize返回一个非空值，而serializers.deserializeWith可以返回一个空值。您可以将返回类型更改为可为空，或者处理serializers.deserializeWith. 如果您愿意，可以使用以下BuiltValueConverter. 他们给出的例子是通用的，只是有微小的变化。

import 'package:built_collection/built_collection.dart';
import 'package:built_value/serializer.dart';
import 'package:chopper/chopper.dart';
import 'package:graphical_representation/app/serializers.dart';

class BuiltValueConverter extends JsonConverter {
  T? _deserialize<T>(dynamic value) => serializers.deserializeWith<T>(
    (serializers.serializerForType(T) as Serializer<T>),
    value,
  );

  BuiltList<T> _deserializeListOf<T>(Iterable value) => BuiltList(
    value.map((value) => _deserialize<T>(value)).toList(growable: false),
  );

  dynamic _decode<T>(entity) {
    /// handle case when we want to access to Map<String, dynamic> directly
    /// getResource or getMapResource
    /// Avoid dynamic or unconverted value, this could lead to several issues
    if (entity is T) return entity;

    try {
      if (entity is List) return _deserializeListOf<T>(entity);
      return _deserialize<T>(entity);
    } catch (e) {
      print(e);
      return null;
    }
  }

  @override
  Response<ResultType> convertResponse<ResultType, Item>(Response response) {
    // use [JsonConverter] to decode json
    final jsonRes = super.convertResponse(response);
    final body = _decode<Item>(jsonRes.body);
    return jsonRes.copyWith<ResultType>(body: body);
  }

  @override
  Request convertRequest(Request request) => super.convertRequest(
    request.copyWith(
      body: serializers.serialize(request.body),
    ),
  );
}
于 2021-09-23T02:35:30.313 回答