domain-layer

name	domain-layer
description	Rules for the domain layer in flutter_starter — Freezed entities with self-owned fromJson, UseCase + Params pattern, and abstract Repository contracts. Use when creating or editing any file under lib/features/*/domain/, or deciding whether a feature needs a separate Model class beyond its Entity.

Domain layer

Entity — default: entity only, owns its own fromJson

Introduce a separate Model only when the API genuinely diverges from the domain (extra fields, renamed keys, type coercion, nested normalisation). If a Model is required, it lives in data/models/ and exposes toEntity().

// lib/features/product/domain/entities/product_entity.dart
@freezed
abstract class ProductEntity with _$ProductEntity {
  const factory ProductEntity({
    required String id,
    required String name,
  }) = _ProductEntity;

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

• Freezed 3.x: always abstract class.
• If the entity is cached in Hive, see the hive-caching skill for @HiveType / @HiveField.

UseCase + Params — one operation per UseCase

• Base class: Usecase<ResultType, Param> from core/shared/usecase.dart.
• Return type is always Future<Either<Failure, ResultType>>.
• Params live in the same file as the UseCase — plain Dart, no HTTP concerns.
• For no-input use cases: Usecase<Result, NoParams> → invoke with NoParams.instance.

// lib/features/order/domain/usecases/create_order_usecase.dart
class CreateOrderParams {
  final String productId;
  final int quantity;
  const CreateOrderParams({required this.productId, required this.quantity});
}

class CreateOrderUseCase extends Usecase<OrderEntity, CreateOrderParams> {
  final OrderRepository _repository;
  CreateOrderUseCase(this._repository);

  @override
  Future<Either<Failure, OrderEntity>> call(CreateOrderParams param) =>
      _repository.create(param);
}

Do not bundle multiple actions. One UseCase = one operation.

Repository — abstract only, in domain/repositories/

// lib/features/order/domain/repositories/order_repository.dart
abstract class OrderRepository {
  Future<Either<Failure, OrderEntity>> create(CreateOrderParams params);
  Future<Either<Failure, List<OrderEntity>>> getAll();
}

The implementation lives in data/ — see the data-layer skill.