(ObjectBox | Dart) 如何将 json 传递给实体类？

Posted 2023-04-19

【中文标题】(ObjectBox | Dart) 如何将 json 传递给实体类？

【英文标题】：(ObjectBox | Dart) How to pass json to entity class?

【发布时间】：2021-10-03 01:13:04

【问题描述】：

JSON 是：

    "name": "Leanne Graham",
    "username": "Bret",
    "email": "[e-mail]",
    "address": 
      "street": "Kulas Light",
      "suite": "Apt. 556",
      "city": "Gwenborough",
      "zipcode": "92998-3874",
      "geo": 
        "lat": "-37.3159",
        "lng": "81.1496"
      
    ,
    "phone": "1-770-736-8031 x56442",
    "website": "hildegard.org",
    "company": 
      "name": "Romaguera-Crona",
      "catchPhrase": "Multi-layered client-server neural-net",
      "bs": "harness real-time e-markets"
    
  

我为 User、Address、Geo、Company 以及这些实体类的扩展做了四个实体类实体 UserModel、AddressModel、GeoModel、CompanyModel，其中每个模型都有 @JsonSerializable 注释以将 JSON 转换为楷模。 现在让我们以地址为例。问题出在我必须将 AddressModel 传递给 User 实体类时 - 首先我在 User 构造函数中没有地址字段，User 类中的第二个地址现在是 final address = ToOne()，这不是地址类型。所以 JsonSerializable 要求我提供 toJson 和 fromJson 到 ToOne 类。

有什么好的例子，我如何使用 json_serializable 包和带有链接对象的对象框，例如这个 json，因为我正在努力解决它？

这里是 JSON 可序列化模型：

@JsonSerializable(explicitToJson: true)
class UserModel extends User 
  final String name;
  final String username;
  final String email;
  final AddressModel address;
  final String phone;
  final String website;
  final CompanyModel company;

  UserModel(
    required this.name,
    required this.username,
    required this.email,
    required this.address,
    required this.phone,
    required this.website,
    required this.company,
  ) : super(
          name: name,
          username: username,
          email: email,
          address: address,
          phone: phone,
          website: website,
          company: company,
        );

  factory UserModel.fromJson(Map<String, dynamic> json) =>
      _$UserModelFromJson(json);
  Map<String, dynamic> toJson() => _$UserModelToJson(this);


// ADDRESS
@JsonSerializable(explicitToJson: true)
class AddressModel extends Address 
  final String street;
  final String suite;
  final String city;
  final String zipcode;
  final GeoModel geo;
  AddressModel(
    required this.street,
    required this.suite,
    required this.city,
    required this.zipcode,
    required this.geo,
  ) : super(
          street: street,
          suite: suite,
          city: city,
          zipcode: zipcode,
          geo: geo,
        );

  factory AddressModel.fromJson(Map<String, dynamic> json) =>
      _$AddressModelFromJson(json);
  Map<String, dynamic> toJson() => _$AddressModelToJson(this);


// COMPANY
@JsonSerializable()
class CompanyModel extends Company 
  final String name;
  final String catchPhrase;
  final String bs;
  CompanyModel(
    required this.name,
    required this.catchPhrase,
    required this.bs,
  ) : super(name: name, catchPhrase: catchPhrase, bs: bs);

  factory CompanyModel.fromJson(Map<String, dynamic> json) =>
      _$CompanyModelFromJson(json);
  Map<String, dynamic> toJson() => _$CompanyModelToJson(this);


// GEO
@JsonSerializable()
class GeoModel extends Geo 
  final String lat;
  final String lng;
  GeoModel(
    required this.lat,
    required this.lng,
  ) : super(lat: lat, lng: lng);

  factory GeoModel.fromJson(Map<String, dynamic> json) =>
      _$GeoModelFromJson(json);
  Map<String, dynamic> toJson() => _$GeoModelToJson(this);

这里是实体类：

class User 
  final String name;
  final String username;
  final String email;
  final Address address;
  final String phone;
  final String website;
  final Company company;

  User(
    required this.name,
    required this.username,
    required this.email,
    required this.address,
    required this.phone,
    required this.website,
    required this.company,
  );


// ADDRESS
class Address 
  final String street;
  final String suite;
  final String city;
  final String zipcode;
  final Geo geo;
  Address(
    required this.street,
    required this.suite,
    required this.city,
    required this.zipcode,
    required this.geo,
  );


// COMPANY
class Company 
  final String name;
  final String catchPhrase;
  final String bs;
  Company(
    required this.name,
    required this.catchPhrase,
    required this.bs,
  );


// GEO
class Geo 
  final String lat;
  final String lng;
  Geo(
    required this.lat,
    required this.lng,
  );

虽然我可以在我的应用程序中使用实体，但我不知道如何使用 ToOne，因此我可以将 User 对象保存在 Objectbox 数据库中，并带有指向 Address、Geo 和 Company 对象的链接。

【问题讨论】：

你能添加一个最小的可重现示例吗？我尝试将 ToOne 关系添加到使用 JsonSerializable() 注释的实体，但它似乎被忽略了，而不是要求转换器。

在Address 上使用? 使可空。我更喜欢freezed 这样做

你在问题​​中提到了JsonSerializable，这就是我提到它的原因。如果你能提供一个最小的代码示例，我可以看看，也许可以帮助你让它工作。

我已经用 JsonSerializable 输入了上面的代码。

我可以帮忙吗？我已经为模型提供了代码示例

【参考方案1】：

这可能是我发现如何将它们组合在一起的方式，但这不是理想的方式，因为在构造函数中清除参数作为 JSON 序列化的实体类结构确实很奇怪。

我希望有一些更清晰的示例，如何使用 ObjectBox 将 JSON 解析为实体类。到目前为止我找不到任何，只是抽象的解释。

@JsonSerializable(explicitToJson: true)
class UserModel extends User 
  final String name;
  final String username;
  final String email;
  final String phone;
  final String website;

  @JsonKey(name: "address")
  final AddressModel ? addressModel;
  @JsonKey(name: "company")
  final CompanyModel ? companyModel;

  UserModel(
    required this.name,
    required this.username,
    required this.email,
    required this.address,
    required this.phone,
    required this.website,
    required this.company,
  ) : super(
          name: name,
          username: username,
          email: email,
          phone: phone,
          website: website,
        )
      this.address.target = addressModel;
      this.company.target = companyModel;
    

  factory UserModel.fromJson(Map<String, dynamic> json) =>
      _$UserModelFromJson(json);
  Map<String, dynamic> toJson() => _$UserModelToJson(this);

@Entity()
class User 
  @JsonKey(ignore: true)
  int id = 0;

  final String name;
  final String username;
  final String email;
  final String phone;
  final String website;

  @JsonKey(ignore: true)
  final address= ToOne<Address>();

  @JsonKey(ignore: true)
  final company= ToOne<Company>();

  User(
    required this.name,
    required this.username,
    required this.email,
    required this.phone,
    required this.website,
  );