(ObjectBox | Dart) How to pass json to entity class?

Question

The JSON is:

{
    "name": "Leanne Graham",
    "username": "Bret",
    "email": "Sincere@april.biz",
    "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"
    }
  }

I Have made four entity classes for User, Address, Geo, Company, and extensions of these entities UserModel, AddressModel, GeoModel, CompanyModel, where each of these models has @JsonSerializable annotation to convert JSON to models. Now lets take Address for example. The problem lies when I have to pass AddressModel to User entity class - first I don't have address field in User constructor, second address in User class is now final address = ToOne(), which is not Address type. So JsonSerializable is asking me to provide toJson and fromJson to ToOne class.

Are there any good examples, how can I use json_serializable package and objectbox with linked objects, for example this json, as I'm struggling to solve it?

Here are JSON serializable Models:

@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);
}

Here are Entity classes:

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,
  });
}

While I can use entities inside my app, I don't know how to use ToOne so I could persist User object in Objectbox database with link to Address, Geo, and Company object.

Can you add a minimal reproducible example? I've tried adding a ToOne relation to an entity annotated with `JsonSerializable()` but it seems to get ignored, instead of asking for converters. — vaind, Jul 27 '21 at 11:58
make nullable using `?` on `Address`. i prefer `freezed` for doing it — Md. Yeasin Sheikh, Jul 27 '21 at 16:03
You're mentioning `JsonSerializable` in the question, that's why I referred to it. If you can provide a minimal code example I could have a look and maybe help you get it working. — vaind, Jul 27 '21 at 17:32
May I please get a help? I have provided code example for models — Edgars Beļevičs, Jul 30 '21 at 15:48

score 2 · Answer 1 · answered Aug 01 '21 at 09:41

This is probably the way I found how I could manage to put them together, but this is not ideal way, as clearing parameters in constructors is really odd as entity class structure for JSON serialization.

I would like to have maybe some clearer example how to parse JSON to entity class using ObjectBox. So far I couldn't find any, just abstract explanations.

@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,
  });
}

(ObjectBox | Dart) How to pass json to entity class?

1 Answers1