Json_serializable.dart: inheritance support

[frickt]

Is inheritance supported? I've tried the following example but got an exception, is there something i miss?:

@JsonSerializable()
abstract class Base extends Object with _$BaseSerializerMixin {
  Base(this.value);

  num value;

  factory Base.fromJson(Map<String, dynamic> json) => _$BaseFromJson(json);
}

@JsonSerializable()
class Sub extends Base with _$SubSerializerMixin {
  Sub(num value, this.subVal): super(value);

  num subVal;

  factory Sub.fromJson(Map<String, dynamic> json) => _$SubFromJson(json);
}

exception thrown:

Unsupported operation: Cannot populate the required constructor argument: value.

[kevmoo]

Remove the @JsonSerialiazble annotation on Base.

[frickt]

No difference, still

Unsupported operation: Cannot populate the required constructor argument: value.

with:

abstract class Base extends Object with _$BaseSerializerMixin {
  Base(this.value);

  num value;

  factory Base.fromJson(Map<String, dynamic> json) => _$BaseFromJson(json);
}

or

abstract class Base {
  Base(this.value);

  num value;

}

[kevmoo]

I just did this w/ the example and it worked great

abstract class ItemCore {
  final int price;

  ItemCore(this.price);
}

@JsonSerializable()
class Item extends ItemCore with _$ItemSerializerMixin {
  int count;
  int itemNumber;
  bool isRushed;

  Item(int price) : super(price);

  factory Item.fromJson(Map<String, dynamic> json) => _$ItemFromJson(json);
}

Does it work for you?

[kevmoo]

run 'pub upgrade' – which version of json_serializable are you using?

On Tue, May 8, 2018 at 11:22 AM frickt [e-mail] wrote:

No difference, still

Unsupported operation: Cannot populate the required constructor argument:
value.

with:

abstract class Base extends Object with _$BaseSerializerMixin {
Base(this.value);

num value;

factory Base.fromJson(Map json) => _$BaseFromJson(json);
}

or

abstract class Base {
Base(this.value);

num value;

}

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[frickt]

Your example has the same issue:

Unsupported operation: Cannot populate the required constructor argument: price.

Maybe, the problem is flutter here, i'm using the configuration described here: https://flutter.io/json/

I did

flutter upgrade
flutter pub upgrade

both had no impact.
my yaml file looks like that:

dependencies:
  flutter:
    sdk: flutter

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.0
  shared_preferences: 0.4.1
  font_awesome_flutter: 6.0.0
  json_annotation: ^0.2.2


dev_dependencies:
  flutter_test:
    sdk: flutter

  build_runner: ^0.7.6
  json_serializable: ^0.3.2

[kevmoo]

That's the issue.

Look here - https://github.com/dart-lang/json_serializable/blob/master/example/pubspec.yaml

You're on old versions. I'll send a PR to fix flutter.io/json

[kevmoo]

PR to fix the site - https://github.com/flutter/website/pull/1017

[spagni]

Kevin thanks for your answer, it was really helpful.

I have one more question. How can we use JsonKey(name: ) in the base class properties.
I'm recieving a json with CamelCase and in my base class properties I'm using lowerCamelCase (as Dart recommends)

I'm having trouble to sort this out.

[kevmoo]

@spagni – would you copy-paste a minimal example for me?

Do you control the base class?

[spagni]

@kevmoo yes I control the base class. I annotated the JsonKey in the base class properties. This is what I ended up doing.

import 'package:json_annotation/json_annotation.dart';

class BaseResponse{
  @JsonKey(name: 'Code')
  int code;
  @JsonKey(name: 'Message')
  String message;

  BaseResponse(this.code, this.message);
}

import 'dataContracts/base_response.dart';
import 'package:json_annotation/json_annotation.dart';

part 'login_response.g.dart';

@JsonSerializable()
class LogInResponse extends BaseResponse with _$LogInResponseSerializerMixin {

  @JsonKey(name: 'ResponseObject', fromJson: _getResponseObject)
  String token;
  LogInResponse(int code, String message) : super(code, message);

  factory LogInResponse.fromJson(Map<String, dynamic> json) => _$LogInResponseFromJson(json);
}

String _getResponseObject(Map<String, dynamic> json) {
  return json['Token'];
}

What are your thoughts on this solution? Is it correct?
Thank you very much for your help

[kevmoo]

Does that seem solution seem reasonable?

On Thu, Aug 2, 2018 at 7:13 PM Sebastian [e-mail] wrote:

@kevmoo https://github.com/kevmoo yes I control the base class. This is
what I ended up doing

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[spagni]

@kevmoo My bad, I've just updated the missing comment

[kevmoo]

What are your thoughts on this solution? Is it correct?

Looks good to me!