OOD design architecture example (no DI container)

no_di_container.dart

/// Data layer

// api
enum Mode {
  mock,
  stage
}

abstract class FireBaseApi {

  factory FireBaseApi(Mode mode) {
    switch (mode) {
      case Mode.mock:
        return FireBaseApi.mock();
      case Mode.stage:
        return FireBaseApi.stage();
    }
    return FireBaseApi.mock();
  }

  factory FireBaseApi.stage() => _FireBaseApi();

  factory FireBaseApi.mock() => _MockApi();

  Stream<List<UserDTO>> users();
}

class _FireBaseApi implements FireBaseApi {
  @override
  Stream<List<UserDTO>> users() {
    return Firestore.instance.collection('users').snapshots().map((snapshot) {
      return snapshot.documents.map((document) {
        final data = document.data;
        return UserDTO()
          ..photoUrl = data['photoUrl']
          ..nickname = data['nickname']
          ..rating = data['rating']
          ..age = data['age']
          ..description = data['description']
          ..height = data['height']
          ..weight = data['weight']
      }).toList();
    });
  }
}

class _MockApi implements FireBaseApi {
  @override
  Stream<List<UserDTO>> users() => Stream.value([]);
}

//repository

class UsersDataRepository implements UsersDomainRepository {
  final FireBaseApi api;

  UsersDataRepository(this.api);

  @override
  Stream<List<UserModel>> users() {
    //UserDto to UserModel code
    return api.users();
  }
}

/// Domain layer

// repository

abstract class UsersDomainRepository {
  Stream<List<UserModel>> users();

  factory UsersDomainRepository.fireCloud() =>
      _UsersDomainRepository(UsersDataRepository(FireBaseApi(Mode.mock)));
}

class _UsersDomainRepository implements UsersDomainRepository {
  final UsersDataRepository repository;

  const _UsersDomainRepository(this.repository);

  @override
  Stream<List<UserModel>> users() => repository.users();
}