Dart - Enterprise v4.0.0

Metadata

Field	Value
Skill Name	moai-lang-dart
Version	4.0.0 (2025-11-12)
Allowed tools	Read, Bash, Context7 MCP
Auto-load	On demand when keywords detected
Tier	Language Enterprise
Context7 Integration	✅ Dart/Flutter/Async/StateManagement

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What It Does

Dart 3.5 enterprise development featuring Flutter 3.24, advanced async programming patterns, modern state management (BLoC, Riverpod, Provider), and enterprise-grade cross-platform mobile development. Context7 MCP integration provides real-time access to official Dart and Flutter documentation.

Key capabilities:

• ✅ Dart 3.5 with advanced type system and patterns
• ✅ Flutter 3.24 enterprise mobile development
• ✅ Advanced async programming with Isolates and Streams
• ✅ Modern state management (BLoC, Riverpod, Provider)
• ✅ Cross-platform development (iOS, Android, Web, Desktop)
• ✅ Enterprise architecture patterns (Clean Architecture, MVVM)
• ✅ Performance optimization and memory management
• ✅ Testing strategies with unit, widget, and integration tests
• ✅ Context7 MCP integration for real-time documentation

---

When to Use

Automatic triggers:

• Dart and Flutter development discussions
• Cross-platform mobile application development
• State management pattern implementation
• Async programming and stream handling
• Mobile app architecture and design
• Enterprise Flutter application development

Manual invocation:

• Design mobile application architecture
• Implement advanced async patterns
• Optimize Flutter app performance
• Review enterprise Dart/Flutter code
• Implement state management solutions
• Troubleshoot mobile development issues

---

Technology Stack (2025-11-12)

Component	Version	Purpose	Status
Dart	3.6.0	Core language	✅ Current
Flutter	3.24.0	UI framework	✅ Current
Riverpod	2.6.1	State management	✅ Current
BLoC	8.1.6	State management	✅ Current
Dio	5.6.0	HTTP client	✅ Current
Provider	6.4.0	State management	✅ Current
Firebase Core	2.28.0	Backend	✅ Current

---

Quick Reference

Null Safety (Dart 3.5)

// Non-nullable by default
String name = 'Alice';

// Nullable with explicit ?
String? email;

// Late initialization
late String value;

// Null-coalescing operator
String display = email ?? 'No email';

// Safe navigation
int? length = email?.length;

Async Programming

// Modern async/await
Future<String> fetchData() async {
  await Future.delayed(Duration(seconds: 1));
  return 'Data';
}

// Stream for continuous values
Stream<int> counter() async* {
  for (int i = 0; i < 5; i++) {
    yield i;
  }
}

// Error handling
try {
  final data = await fetchData();
} catch (e) {
  print('Error: $e');
}

Flutter Widgets

// StatelessWidget - immutable UI
class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) => Text('Hello');
}

// StatefulWidget - mutable state
class Counter extends StatefulWidget {
  @override
  State<Counter> createState() => _CounterState();
}

class _CounterState extends State<Counter> {
  int count = 0;

  @override
  Widget build(BuildContext context) {
    return FloatingActionButton(
      onPressed: () => setState(() => count++),
      child: Text('$count'),
    );
  }
}

State Management Pattern Selection

Simple UI          → setState
Single Feature     → Provider / GetX
Complex App        → Riverpod / BLoC
Enterprise Scale   → BLoC + Repository Pattern

---

Implementation Patterns

Pattern 1: Null Safety Best Practices

// Type safety ensures null checks at compile time
class User {
  final String id;
  final String? optionalEmail;

  User({required this.id, this.optionalEmail});

  // Safe method with null-coalescing
  String getEmail() => optionalEmail ?? '[email protected]';

  // Null-aware property access
  bool hasEmail() => optionalEmail?.isNotEmpty ?? false;
}

// Usage ensures type safety
final user = User(id: '1', optionalEmail: '[email protected]');
print(user.getEmail());     // Type-safe string
print(user.hasEmail());     // Type-safe boolean

Pattern 2: Async Stream Handling

// Generator function for streams
Stream<String> dataStream() async* {
  for (int i = 0; i < 5; i++) {
    yield 'Item $i';
    await Future.delayed(Duration(seconds: 1));
  }
}

// Listening with error handling
dataStream().listen(
  (value) => print(value),
  onError: (error) => print('Error: $error'),
  onDone: () => print('Complete'),
  cancelOnError: false,
);

Pattern 3: Provider State Management

// Simple provider for state
class CounterProvider extends ChangeNotifier {
  int _count = 0;
  int get count => _count;

  void increment() {
    _count++;
    notifyListeners();
  }
}

// Using Provider in widget
Consumer<CounterProvider>(
  builder: (context, counter, child) {
    return Text('Count: ${counter.count}');
  },
)

Pattern 4: Repository Pattern

// Data layer abstraction
abstract class UserRepository {
  Future<User> getUser(String id);
  Future<void> saveUser(User user);
}

// Implementation
class UserRepositoryImpl implements UserRepository {
  final apiClient = ApiClient();

  @override
  Future<User> getUser(String id) async {
    final response = await apiClient.get('/users/$id');
    return User.fromJson(response);
  }

  @override
  Future<void> saveUser(User user) async {
    await apiClient.post('/users', data: user.toJson());
  }
}

Pattern 5: Widget Architecture

// Composition-based widget tree
class AppScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Title')),
      body: ListView(
        children: [
          HeaderSection(),
          ContentSection(),
          FooterSection(),
        ],
      ),
    );
  }
}

---

Advanced Topics

Error Handling Strategy

User Input    → Validation errors → Show in UI
Network Call  → Timeout/connection → Retry with exponential backoff
Data Parse    → Format errors → Log and use default
State Update  → Concurrent updates → Use immutable state pattern

Performance Optimization

• Use const constructors for immutable widgets
• Implement ListView.builder instead of ListView for large lists
• Cache expensive computations with memoization
• Profile with DevTools to identify bottlenecks
• Use RepaintBoundary for complex widget trees

Testing Strategy

• Unit Tests: Business logic (90%+ coverage target)
• Widget Tests: UI components and interactions
• Integration Tests: Full user flows and scenarios
• Mocking: External dependencies with Mockito

---

Common Use Cases

Mobile App with API Integration

1. Define models and repository layer
2. Implement state management (Riverpod/Provider)
3. Create service layer for API calls
4. Build UI widgets consuming state
5. Add comprehensive error handling
6. Test with mocks and fixtures

Cross-Platform App (iOS + Android + Web)

1. Use Flutter for shared UI code
2. Platform channels for native code
3. State management for feature consistency
4. Responsive design with MediaQuery
5. Test on all target platforms

Real-Time Data (Streams)

1. Define stream-based providers
2. Listen to data updates in UI
3. Implement unsubscribe on disposal
4. Handle connection errors gracefully
5. Buffer/throttle high-frequency updates

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Enterprise Checklist

• Null safety enabled (sdk: '>=3.0.0')
• Clean architecture with separation of concerns
• Repository pattern for data access
• State management with proper scoping
• Comprehensive error handling
• Logging and monitoring in place
• Unit test coverage ≥85%
• Widget tests for critical UI
• Integration tests for key flows
• Performance profiling completed
• Security review (data encryption, API auth)
• Documentation and code examples provided
• CI/CD pipeline configured
• Crash reporting integrated

---

Common Pitfalls

❌ Avoid

// Throwing unhandled exceptions
Future<Data> fetchData() async => apiCall();  // No error handling

// Memory leaks in streams
controller.stream.listen(...);  // Not cancelled

// Mutable state in build()
int counter = 0;  // Recreated on each build

✅ Do Instead

// Handle errors gracefully
Future<Data> fetchData() async {
  try { return await apiCall(); }
  catch (e) { return Data.empty(); }
}

// Cancel subscriptions
StreamSubscription sub = stream.listen(...);
@override void dispose() { sub.cancel(); }

// Use State/Provider for mutable data
class Counter extends StatefulWidget { ... }

---

Resources

Official Documentation:

• Dart Guide: https://dart.dev
• Flutter Guide: https://flutter.dev
• Packages: https://pub.dev

Learning:

• Effective Dart: https://dart.dev/guides/language/effective-dart
• Flutter Codelabs: https://flutter.dev/codelabs
• Riverpod Tutorial: https://riverpod.dev

Tools:

• Flutter DevTools: DevTools for debugging
• Dart Analyzer: Static analysis
• Coverage Tools: lcov for coverage reporting

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Context7 Integration

This skill integrates with Context7 MCP for real-time documentation:

Keyword Detection → Context7 Query → Real-Time API Docs
  "async/await"   → Dart async guide
  "Flutter widget" → Flutter widget docs
  "Riverpod"     → Riverpod state management
  "Firebase"     → Firebase integration guide

Enable with: mcp__context7__resolve-library-id + mcp__context7__get-library-docs

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Version History

Version	Date	Status	Notes
4.0.0	2025-11-12	Current	Enterprise v4 restructure, Context7 integration
3.5.4	2025-10-22	Previous	Advanced patterns focus
3.0.0	2025-09-01	Legacy	Initial release

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For detailed examples → See examples.md For API reference → See reference.md For hands-on patterns → See examples.md Part 3-4