Flutter Retrofit Networking

Retrofit & Dio Networking

Priority: P0 (CRITICAL)

Type-safe REST API communication using Dio and Retrofit.

Structure

infrastructure/
├── data_sources/
│   ├── remote/ # Retrofit abstract classes
│   └── local/ # Cache/Storage
└── network/
    ├── dio_client.dart # Custom Dio setup
    └── interceptors/ # Auth, Logging, Cache

Implementation Guidelines

• Retrofit Clients: Define abstract classes with @RestApi(). Use standard HTTP annotations (@GET('/route'), @POST('/route/{id}/cancel') with @Path('id')). Methods must return Future<DTO>.
• DTOs (Data Transfer Objects): Use @freezed and @JsonSerializable for all response/request bodies.
• Mapping: Data sources MUST map DTOs to Domain Entities (e.g., userDto.toDomain()).
• Safe Enums: Always use @JsonKey(unknownEnumValue: OrderStatus.unknown) for DTO enums with an unknown fallback value to prevent crashes when the backend introduces new values.
• AuthInterceptor: Logic for Authorization: Bearer <token> injection in onRequest.
• Token Refresh: Handle 401 Unauthorized in onError by checking DioException, locking Dio, calling refreshToken(), updating the stored token, and retrying via dio.fetch(err.requestOptions).
• Failures: Map DioException to custom Failure objects (ServerFailure, NetworkFailure).

Anti-Patterns

• No Manual JSON Parsing: Do not use jsonDecode(response.body); use Retrofit's generated mappers.
• No Global Dio: Do not use a static global Dio instance; use dependency injection.
• No Try-Catch in API: Do not put try-catch inside the Retrofit interface methods.
• No Unsafe Enums: Do not leave enums in DTOs without handling unknown values from the server.

Reference & Examples

For RestClient definitions and Auth Interceptor implementation: See references/REFERENCE.md.

Related Topics

feature-based-clean-architecture | error-handling