flutter_domain_data_layer

🎯 Domain Layer (Business Logic)

Purpose: Define business rules and domain models

Components:

• Models: Pure business entities (no dependencies)
• Use Cases: Business logic operations (optional for simpler apps)

Rules:

1. Models MUST be pure Dart classes
2. Models MUST NOT depend on Flutter SDK
3. Models MUST NOT depend on external packages (except code generation annotations like freezed_annotation)
4. Models SHOULD be immutable when possible
5. Models SHOULD use value equality (prefer freezed for this)

Example Domain Model (with Freezed)

// ✅ CORRECT: Pure, immutable, uses Freezed for value equality and copyWith
import 'package:freezed_annotation/freezed_annotation.dart';

part 'booking.freezed.dart';

@freezed
class Booking with _$Booking {
  const factory Booking({
    required String id,
    required String userId,
    required String destination,
    required DateTime startDate,
    required DateTime endDate,
    required BookingStatus status,
  }) = _Booking;

  // Custom getters/methods can be added by adding a private constructor
  const Booking._();

  bool get isActive => status == BookingStatus.confirmed || status == BookingStatus.pending;
}

enum BookingStatus {
  pending,
  confirmed,
  cancelled,
  completed,
}

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🎯 Data Layer (Data Access)

Purpose: Fetch, cache, and manage data from external sources

Components:

• Repositories: Coordinate data from multiple sources
• Services: Handle specific external APIs or system features
• Data Models: API-specific models with serialization

Rules:

1. Repositories MUST extend BaseRepository (if available)
2. Repositories MUST return Result<T> types (see flutter_design_patterns.mdc)
3. Repositories MUST handle all exceptions
4. Repositories SHOULD cache data when appropriate
5. Services MUST be injected into repositories
6. Services MUST NOT be used directly by ViewModels
7. Data models MUST include serialization (toJson/fromJson), prefer json_serializable or freezed