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android - 无法将 Json 序列化为内部具有列表对象的对象 (DART)

问题描述

序列化时出现错误。控制台日志说：

> NoSuchMethodError: Class 'String' has no instance method 'forEach'.
> Receiver: "no" Tried calling: forEach(Closure: (dynamic) => Null) dan
> 0      Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
> 1      new Article.fromJson (package:tribun_travel/model/article.dart:84:19)
> 2      new ResponseRead.fromJson (package:tribun_travel/model/response_read.dart:16:39)
> 3      BlogRepository.readNewsById (package:tribun_travel/repositories/blog_repository.dart:21:25)
> <asynchronous suspension>
> 4      BlogBloc.mapEventToState (package:tribun_travel/bloc/blog_bloc.dart:28:61) <asynchronous
> suspension>

我所做的是，我想json在 Dart 中对 Object 进行序列化。在我的班级里面有列表对象。片段代码如下所示：

class ResponseRead {
  String status;
  String message;
  String source;
  Article data;

  ResponseRead({this.status, this.message, this.source, this.data});

  ResponseRead.fromJson(Map<String, dynamic> json) {
    status = json['status'];
    message = json['message'];
    source = json['source'];
    data = json['data'] != null ? new Article.fromJson(json['data']) : null;
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['status'] = this.status;
    data['message'] = this.message;
    data['source'] = this.source;
    if (this.data != null) {
      data['data'] = this.data.toJson();
    }
    return data;
  }
}

class Article{

  String id;
  String fulltexts;
  List<Tag> tag;
  List<Related> related;

  Article(
      {this.id,
        this.fulltexts,
        this.tag,
        this.related
      });

  Article.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    fulltexts = json['fulltexts'];
    if (json['tag'] != null) {

      tag = new List<Tag>();
      json['tag'].forEach((v) {
        tag.add(new Tag.fromJson(v));
      });
    }
    if (json['related'] != null) {

      related = new List<Related>();
      json['related'].forEach((v) {
        related.add(new Related.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['fulltexts'] = this.fulltexts;
    if (this.tag != null) {
      data['tag'] = this.tag.map((v) => v.toJson()).toList();
    }
    if (this.related != null) {
      data['related'] = this.related.map((v) => v.toJson()).toList();
    }
    return data;
  }

  @override
  String toString() {
    return 'Article{id: $id, title: $title, photo: $photo}';
  }
}

我认为我的服务没有问题，因为它返回了我想要的。但是，为什么我在序列化时仍然有错误？

更新 这是我的示例 Json 文件

{
    "status": "success",
    "message": "Found",
    "source": "memcached",
    "article": {
        "title": "Ini Alasan Pramugari Jarang Sakit Meski Terbang Berjam-jam",
        "fulltexts": "<p><</p>",
        "tag": [
            {
                "id": "1",
                "title": "a",
                "alias": "a"
            },
            {
                "id": "2",
                "title": "b",
                "alias": "b"
            }
        ],
        "related": [
            {
                "id": "79224",
            },
            {
                "id": "79219",
            }
        ]
    }
}

标签： androidflutterserializationdart

解决方案

问题可能是您希望 JSON 中的json['related']orjson['tag']是一个列表，但它实际上是一个字符串。检查实际的 JSON 文本，您可能会发现"related": "some string"，不是"related": []

请发布实际的 JSON，以便我们找到。

谢谢

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