Flutter DDD Patterns

Flutter DDD Patterns

Architecture Overview

lib/apps/
├── domain/{domain}/
│   ├── models/         # {entity}_model.dart (Freezed 3.x)
│   ├── services/       # {domain}_service.dart (Riverpod 3.x AsyncNotifier)
│   ├── pages/{page}/
│   │   ├── {page}_page.dart
│   │   └── providers/  # {feature}_provider.dart
│   └── components/
├── infra/              # Dio client, interceptors, exception
├── application/        # Cross-feature (storage, auth)
├── ui/                 # theme, router, common components
├── generated/api/      # swagger_parser output (수동 편집 금지)
└── global/             # constants, utils, hooks, types

Core Rules:

• No Repository/DataSource — Provider → Dio 직접 호출
• No DTO/Entity 분리 — 모든 모델은 _model.dart + Model suffix
• Freezed 3.x @freezed abstract class + const factory
• Riverpod 3.x @riverpod + Ref (not FooRef)
• Always package:app/... imports (no relative)

Quick Reference Checklists

Freezed Model

• @freezed annotation
• abstract class {Entity}Model with _${Entity}Model
• const {Entity}Model._(); (custom methods가 있을 때)
• const factory constructor (const 필수)
• fromJson factory
• Part files: .freezed.dart + .g.dart
• 파일명 {entity}_model.dart, 절대 _dto.dart 아님

Riverpod Provider/Service

• @riverpod annotation (lowercase)
• Class: extends _${Name} | Function: Ref ref parameter
• build() 안에서만 ref.watch — helper/action 메서드에서는 ref.read
• AsyncValue.guard for error handling
• UI 상태 반응은 Page의 build()에서 ref.listen 사용

Router (go_router)

• 정적 경로(/posts/new)를 동적 경로(/posts/:id) 앞에 등록
• Route class: static const path, static const name, go(), push()
• RouterClient: abstract final class with const instances

Auth State Management

• authProvider 로그인 실패 시 AsyncData(unauthenticated()) 복귀 (절대 AsyncError 아님)
• 에러 전파: Error.throwWithStackTrace(e, st) (rethrow 대신 — 상태 설정 후 전파)
• emailLoginProvider가 에러 메시지 담당 (역할 분리)
• Login UI: ref.listen(authProvider) → 성공 네비게이션, ref.listen(emailLoginProvider) → 에러 표시
• 에러 메시지: AppException → ExceptionHandler.getUserMessage(), 그 외 → generic 메시지
• Router redirect: authValue == null → 미인증 취급 (defense-in-depth)

Auth Interceptor

• Retry Dio에 ResponseInterceptor + ErrorInterceptor 포함
• AuthInterceptor는 retry Dio에서 제외 (무한루프 방지)
• 로그인 시 refreshToken 저장 확인

Pagination

• PaginatedResponse<T> model in lib/global/types/paginated_response.dart
• PaginationMeta with offset/pageSize/totalItemCount/isFirst/isLast
• Provider uses _page counter + _hasMore flag
• loadMore() appends to existing list
• UI uses NotificationListener<ScrollNotification> or ScrollController

AsyncValueWidget

• Use AsyncValueWidget instead of .when(data:, error:, loading:) inline
• Located at lib/apps/ui/common/async_value_widget.dart
• Supports emptyCheck and emptyMessage for empty states
• Custom loading and error builders optional

Form Validation

• Use Validators from lib/global/utils/validators.dart
• Validators.compose([...]) for multiple rules
• Available: required, email, minLength, maxLength, phone, password

Loading Overlay

• withLoaderOverlay(context, () async { ... }) for button actions
• Requires LoaderOverlay widget in tree (wrap Scaffold or MaterialApp)
• Auto-hides on success or error

Theme (Dual Mode)

• AppTheme.fromTokens() — Figma token-based (AppColors → ColorScheme)
• AppTheme.fromSeed(seedColor: Colors.blue) — Material 3 auto-generated
• Both modes: Theme.of(context).colorScheme.primary works identically
• AppSpacing, AppRadius usable in both modes

Naming Conventions

Import Order

import 'dart:async';                                   // 1. Dart
import 'package:freezed_annotation/freezed_annotation.dart'; // 2. Package
import 'package:app/apps/domain/.../model.dart';       // 3. Project (absolute)
part 'file.g.dart';                                    // 4. Part

Code Generation

dart run swagger_parser                                    # API clients
dart run build_runner build --delete-conflicting-outputs   # Freezed + Riverpod

Detailed References

• Freezed 3.x Guide — Union types, nested models, enums, custom JSON, testing
• Riverpod 3.x Guide — AsyncNotifier, provider types, family, ref.watch vs ref.read
• API Client Patterns — CRUD, pagination, file upload, error handling
• Anti-Patterns — 10가지 금지 패턴 + Auth Interceptor 올바른 패턴

Working Examples

• user_model_example.dart — Freezed model with custom methods
• auth_service_example.dart — Riverpod AsyncNotifier service
• post_create_page_example.dart — ref.listen UI 상태 처리
• paginated_list_example.dart — Pagination Provider + infinite scroll UI
• form_with_validation_example.dart — Validators + withLoaderOverlay