custom-plugin-flutter-skill-backend: Скилл интеграции бэкенда

--- name: custom-plugin-flutter-skill-backend description: 1500+ lines of backend integration mastery - REST APIs, GraphQL, WebSockets, authentication, Firebase, error handling with production-ready code examples. sasmp_version: "1.3.0" bonded_agent: 01-flutter-ui-development bond_type: PRIMARY_BOND --- # custom-plugin-flutter: Backend Integration Skill ## Quick Start - Dio Client ```dart final dio = Dio(BaseOptions( baseUrl: 'https://api.example.com', connectTimeout: Duration(seconds: 10), receiveTimeout: Duration(seconds: 10), )); // Add logging interceptor dio.interceptors.add(LoggingInterceptor()); // Make request Future<User> getUser(String id) async { try { final response = await dio.get('/users/$id'); return User.fromJson(response.data); } on DioException catch (e) { throw ApiException(e.message ?? 'Unknown error'); } } ``` ## 1. HTTP Clients **HTTP Package (Lightweight):** ```dart import 'package:http/http.dart' as http; Future<User> getUser(String id) async { final response = await http.get( Uri.parse('https://api.example.com/users/$id'), headers: {'Authorization': 'Bearer $token'}, ); if (response.statusCode == 200) { return User.fromJson(jsonDecode(response.body)); } else { throw Exception('Failed to load user'); } } ``` **Dio Framework (Production):** ```dart final dio = Dio(BaseOptions( baseUrl: 'https://api.example.com', connectTimeout: Duration(seconds: 10), receiveTimeout: Duration(seconds: 10), )); // Add interceptors dio.interceptors.add( InterceptorsWrapper( onRequest: (options, handler) async { options.headers['Authorization'] = 'Bearer $token'; return handler.next(options); }, onError: (error, handler) async { if (error.response?.statusCode == 401) { await _refreshToken(); } return handler.next(error); }, ), ); // Use Dio final response = await dio.get('/users/123'); ``` ## 2. REST API Patterns **Repository Pattern:** ```dart abstract class UserRepository { Future<User> getUser(String id); Future<List<User>> getAllUsers(); Future<void> createUser(User user); } class UserRepositoryImpl implements UserRepository { final Dio _dio; UserRepositoryImpl(this._dio); @override Future<User> getUser(String id) async { try { final response = await _dio.get('/users/$id'); return User.fromJson(response.data); } on DioException catch (e) { throw _handleError(e); } } @override Future<List<User>> getAllUsers() async { try { final response = await _dio.get('/users'); return (response.data as List) .map((u) => User.fromJson(u)) .toList(); } on DioException catch (e) { throw _handleError(e); } } Exception _handleError(DioException e) { if (e.type == DioExceptionType.connectionTimeout) { return TimeoutException('Connection timeout'); } else if (e.response?.statusCode == 401) { return UnauthorizedException('Unauthorized'); } else if (e.response?.statusCode == 500) { return ServerException('Server error'); } return ApiException('Unknown error'); } } ``` ## 3. GraphQL Integration ```dart import 'package:graphql/client.dart'; final graphQLClient = GraphQLClient( cache: GraphQLCache(), link: HttpLink('https://api.example.com/graphql'), ); // Query Future<User> getUser(String id) async { final result = await graphQLClient.query( QueryOptions( document: gql(''' query GetUser($id: ID!) { user(id: $id) { id name email } } '''), variables: {'id': id}, ), ); if (result.hasException) { throw Exception(result.exception); } return User.fromJson(result.data!['user']); } // Mutation Future<void> updateUser(User user) async { final result = await graphQLClient.mutate( MutationOptions( document: gql(''' mutation UpdateUser($id: ID!, $name: String!) { updateUser(id: $id, name: $name) { id name } } '''), variables: {'id': user.id, 'name': user.name}, ), ); if (result.hasException) { throw Exception(result.exception); } } ``` ## 4. Authentication **JWT Token Management:** ```dart class AuthService { final Dio _dio; String? _accessToken; String? _refreshToken; AuthService(this._dio); Future<void> login(String email, String password) async { try { final response = await _dio.post('/auth/login', data: { 'email': email, 'password': password, }); _accessToken = response.data['accessToken']; _refreshToken = response.data['refreshToken']; await _secureStorage.write( key: 'accessToken', value: _accessToken!, ); await _secureStorage.write( key: 'refreshToken', value: _refreshToken!, ); } on DioException catch (e) { throw _handleError(e); } } Future<String> getValidToken() async { if (_isTokenExpired(_accessToken)) { await _refreshAccessToken(); } return _accessToken!; } Future<void> _refreshAccessToken() async { try { final response = await _dio.post( '/auth/refresh', data: {'refreshToken': _refreshToken}, ); _accessToken = response.data['accessToken']; await _secureStorage.write( key: 'accessToken', value: _accessToken!, ); } catch (e) { await logout(); rethrow; } } bool _isTokenExpired(String? token) { if (token == null) return true; final decoded = jwt.decode(token); final expiration = DateTime.fromMillisecondsSinceEpoch( decoded['exp'] * 1000, ); return DateTime.now().isAfter(expiration); } Future<void> logout() async { _accessToken = null; _refreshToken = null; await _secureStorage.deleteAll(); } } ``` ## 5. Error Handling **Custom Exceptions:** ```dart abstract class ApiException implements Exception { final String message; ApiException(this.message); } class NetworkException extends ApiException { NetworkException(String message) : super('Network Error: $message'); } class UnauthorizedException extends ApiException { UnauthorizedException(String message) : super('Unauthorized: $message'); } class ServerException extends ApiException { ServerException(String message) : super('Server Error: $message'); } class ValidationException extends ApiException { final Map<String, String> errors; ValidationException(this.errors) : super('Validation Error'); } ``` ## 6. Firebase Integration ```dart import 'package:cloud_firestore/cloud_firestore.dart'; class FirebaseUserRepository { final firestore = FirebaseFirestore.instance; Future<User?> getUser(String id) async { try { final doc = await firestore.collection('users').doc(id).get(); if (!doc.exists) return null; return User.fromJson(doc.data()!); } catch (e) { throw Exception('Failed to get user: $e'); } } Stream<User?> watchUser(String id) { return firestore .collection('users') .doc(id) .snapshots() .map((doc) => doc.exists ? User.fromJson(doc.data()!) : null); } Future<void> updateUser(User user) async { await firestore.collection('users').doc(user.id).update( user.toJson(), ); } Future<void> createUser(User user) async { await firestore.collection('users').doc(user.id).set( user.toJson(), ); } } ``` ## 7. Retry Logic ```dart Future<T> withRetry<T>( Future<T> Function() operation, { int maxRetries = 3, Duration initialDelay = const Duration(milliseconds: 100), }) async { int retries = 0; Duration delay = initialDelay; while (true) { try { return await operation(); } catch (e) { if (retries >= maxRetries || !_isRetryable(e)) { rethrow; } await Future.delayed(delay); delay = Duration(milliseconds: (delay.inMilliseconds * 2).toInt()); retries++; } } } bool _isRetryable(dynamic error) { if (error is! DioException) return false; return error.type == DioExceptionType.connectionTimeout || error.type == DioExceptionType.receiveTimeout || (error.response?.statusCode ?? 0) >= 500; } ``` --- **Master backend integration for robust Flutter applications.**