sealed_unions_annotations #

Sealed Unions Annotations works together with Sealed Unions Generator to generate the boiler plate for your state models.

How to use #

pubspec.yaml of your plugin

dependencies:
  sealed_unions_annotations: ^0.0.1
    
    
dev_dependencies:
  build_runner: ^1.6.5
  sealed_unions_generator: ^0.0.1

You write this

import 'package:sealed_unions_annotations/sealed_unions_annotations.dart';
import 'package:sealed_unions/sealed_unions.dart';

part 'weather_model.g.dart';
@Seal('WeatherState')
abstract class WeatherModel {
  @Sealed()
  void initial();
  @Sealed()
  void loading();
  @Sealed()
  void loaded(int temperature);

}

You run the command

flutter pub run build_runner build      

and the project writes this:

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'weather_model.dart';

// **************************************************************************
// SealedUnionsGenerator
// **************************************************************************

class WeatherState extends Union3Impl<WeatherStateInitial, WeatherStateLoading,
    WeatherStateLoaded> {
  static final Triplet<WeatherStateInitial, WeatherStateLoading,
          WeatherStateLoaded> _factory =
      const Triplet<WeatherStateInitial, WeatherStateLoading,
          WeatherStateLoaded>();

  WeatherState._(
      Union3<WeatherStateInitial, WeatherStateLoading, WeatherStateLoaded>
          union)
      : super(union);

  factory WeatherState.initial() =>
      WeatherState._(_factory.first(WeatherStateInitial()));

  factory WeatherState.loading() =>
      WeatherState._(_factory.second(WeatherStateLoading()));

  factory WeatherState.loaded(int temperature) =>
      WeatherState._(_factory.third(WeatherStateLoaded(temperature)));
}

class WeatherStateInitial {
  WeatherStateInitial();
}

class WeatherStateLoading {
  WeatherStateLoading();
}

class WeatherStateLoaded {
  final int temperature;

  WeatherStateLoaded(this.temperature);
}

The command will create WeatherState class and that class will have factories to control the state. You won't access your class WeatherModel, but the generated one to control the state. This is a downside of this project and I have not found a solution for this.

Use WeatherState.initial(), WeatherState.loading() and WeatherState.loaded(1) directly as there is no point to hide it behind WeatherState since you will need to use WeatherState.join(A,B,C).