docs(rest_api): add example for REST Api handling

examples/rest_api/.metadata

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+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: "17025dd88227cd9532c33fa78f5250d548d87e9a"
+  channel: "stable"
+
+project_type: app
+
+# Tracks metadata for the flutter migrate command
+migration:
+  platforms:
+    - platform: root
+      create_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+      base_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+    - platform: android
+      create_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+      base_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+    - platform: ios
+      create_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+      base_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+    - platform: linux
+      create_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+      base_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+    - platform: macos
+      create_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+      base_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+    - platform: web
+      create_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+      base_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+    - platform: windows
+      create_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+      base_revision: 17025dd88227cd9532c33fa78f5250d548d87e9a
+
+  # User provided section
+
+  # List of Local paths (relative to this file) that should be
+  # ignored by the migrate tool.
+  #
+  # Files that are not part of the templates will be ignored by default.
+  unmanaged_files:
+    - 'lib/main.dart'
+    - 'ios/Runner.xcodeproj/project.pbxproj'

examples/rest_api/README.md

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+# REST API Example
+
+A simple example demonstrating how to handle REST APIs with Riverpod, including proper testing practices.
+
+## Key Points
+
+This example demonstrates how to:
+
+- Implement a REST API client with proper error handling
+- Manage async state with AsyncNotifier
+- Handle loading and error states
+- Perform CRUD operations (Create and Read)
+- Write comprehensive tests for all layers
+- Use modern Dart patterns like pattern matching
+- Implement form validation
+- Handle pull-to-refresh
+
+## Code Structure
+
+- `lib/main.dart` - Contains all the code for simplicity
+  - User model with JSON serialization
+  - Repository for API communication
+  - State management with AsyncNotifier
+  - UI with proper error and loading states
+
+- `test/user_test.dart` - Repository and state management tests
+- `test/widget_test.dart` - Widget tests
+
+## Testing
+
+The example includes tests for:
+
+- Repository layer (API calls)
+- State management (AsyncNotifier)
+- Widget behavior
+- Form validation
+- Error handling
+
+Run tests with:
+
+```bash
+flutter test
+```

examples/rest_api/analysis_options.yaml

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+# This file configures the analyzer, which statically analyzes Dart code to
+# check for errors, warnings, and lints.
+#
+# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
+# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
+# invoked from the command line by running `flutter analyze`.
+
+# The following line activates a set of recommended lints for Flutter apps,
+# packages, and plugins designed to encourage good coding practices.
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  # The lint rules applied to this project can be customized in the
+  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
+  # included above or to enable additional rules. A list of all available lints
+  # and their documentation is published at https://dart.dev/lints.
+  #
+  # Instead of disabling a lint rule for the entire project in the
+  # section below, it can also be suppressed for a single line of code
+  # or a specific dart file by using the `// ignore: name_of_lint` and
+  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
+  # producing the lint.
+  rules:
+    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
+    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

examples/rest_api/lib/main.dart

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+import 'package:dio/dio.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+void main() {
+  runApp(ProviderScope(child: MyApp()));
+}
+
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      home: UserListScreen(),
+    );
+  }
+}
+
+// Model class representing a User with JSON serialization
+class User {
+  final int id;
+  final String name;
+  final String email;
+
+  User({required this.id, required this.name, required this.email});
+
+  // Factory constructor for JSON deserialization
+  factory User.fromJson(Map<String, dynamic> json) => User(
+        id: json['id'],
+        name: json['name'],
+        email: json['email'],
+      );
+
+  // Method for JSON serialization
+  Map<String, dynamic> toJson() => {
+        'id': id,
+        'name': name,
+        'email': email,
+      };
+}
+
+// Repository class handling API communications
+class UserRepository {
+  final Dio dio;
+
+  UserRepository(this.dio);
+
+  // Fetches all users from the API
+  Future<List<User>> fetchUsers() async {
+    try {
+      final response =
+          await dio.get('https://jsonplaceholder.typicode.com/users');
+      return (response.data as List)
+          .map((userData) => User.fromJson(userData))
+          .toList();
+    } catch (e) {
+      throw Exception('Failed to load users');
+    }
+  }
+
+  // Creates a new user via API
+  Future<User> createUser(User user) async {
+    try {
+      final response = await dio.post(
+        'https://jsonplaceholder.typicode.com/users',
+        data: user.toJson(),
+      );
+      return User.fromJson(response.data);
+    } catch (e) {
+      throw Exception('Failed to create user');
+    }
+  }
+}
+
+// Dependency injection setup using Riverpod providers
+final dioProvider = Provider((ref) => Dio());
+
+final userRepositoryProvider = Provider((ref) {
+  return UserRepository(ref.watch(dioProvider));
+});
+
+// Main state provider for the users list
+final usersProvider = AsyncNotifierProvider<UsersNotifier, List<User>>(() {
+  return UsersNotifier();
+});
+
+// State management class for Users
+class UsersNotifier extends AsyncNotifier<List<User>> {
+  @override
+  Future<List<User>> build() async {
+    final repository = ref.watch(userRepositoryProvider);
+    return repository.fetchUsers();
+  }
+
+  Future<void> addUser(User user) async {
+    final repository = ref.watch(userRepositoryProvider);
+    state = const AsyncValue.loading();
+    state = await AsyncValue.guard(() async {
+      final newUser = await repository.createUser(user);
+      // Get current users and add the new one
+      final currentUsers = state.value ?? [];
+      return [...currentUsers, newUser];
+    });
+  }
+}
+
+// Main screen showing the list of users
+class UserListScreen extends ConsumerWidget {
+  const UserListScreen({super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    // Watch the users state for changes
+    final usersAsync = ref.watch(usersProvider);
+
+    return Scaffold(
+      appBar: AppBar(title: const Text('Users')),
+      floatingActionButton: FloatingActionButton(
+        onPressed: () => Navigator.push(
+          context,
+          MaterialPageRoute(builder: (context) => const AddUserScreen()),
+        ),
+        child: const Icon(Icons.add),
+      ),
+      // Using Dart 3's pattern matching with switch expression
+      // This handles all possible states of AsyncValue:
+      // - AsyncData: When we have the data
+      // - AsyncError: When an error occurred
+      // - _: Wildcard for loading and any other state
+      body: switch (usersAsync) {
+        AsyncData(:final value) => RefreshIndicator(
+            onRefresh: () => ref.refresh(usersProvider.future),
+            child: ListView.builder(
+              itemCount: value.length,
+              itemBuilder: (context, index) {
+                final user = value[index];
+                return ListTile(
+                  title: Text(user.name),
+                  subtitle: Text(user.email),
+                );
+              },
+            ),
+          ),
+        AsyncError(:final error) => Center(child: Text('Error: $error')),
+        _ => const Center(child: CircularProgressIndicator()),
+      },
+    );
+  }
+}
+
+// Screen for adding a new user
+class AddUserScreen extends ConsumerStatefulWidget {
+  const AddUserScreen({super.key});
+
+  @override
+  AddUserScreenState createState() => AddUserScreenState();
+}
+
+class AddUserScreenState extends ConsumerState<AddUserScreen> {
+  // Form key for validation
+  final _formKey = GlobalKey<FormState>();
+  // Controllers for form fields
+  final _nameController = TextEditingController();
+  final _emailController = TextEditingController();
+
+  // Clean up controllers when the widget is disposed
+  @override
+  void dispose() {
+    _nameController.dispose();
+    _emailController.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    // Function to pop the context to avoid using
+    //context across async gaps
+    void popContext() {
+      Navigator.pop(context);
+    }
+
+    return Scaffold(
+      appBar: AppBar(title: const Text('Add User')),
+      body: Padding(
+        padding: const EdgeInsets.all(16.0),
+        child: Form(
+          key: _formKey,
+          child: Column(
+            children: [
+              // Name input field with validation
+              TextFormField(
+                controller: _nameController,
+                decoration: const InputDecoration(labelText: 'Name'),
+                validator: (value) {
+                  if (value == null || value.isEmpty) {
+                    return 'Please enter a name';
+                  }
+                  return null;
+                },
+              ),
+              // Email input field with validation
+              TextFormField(
+                controller: _emailController,
+                decoration: const InputDecoration(labelText: 'Email'),
+                validator: (value) {
+                  if (value == null || value.isEmpty) {
+                    return 'Please enter an email';
+                  }
+                  if (!value.contains('@')) {
+                    return 'Please enter a valid email';
+                  }
+                  return null;
+                },
+              ),
+              const SizedBox(height: 16),
+              ElevatedButton(
+                onPressed: () async {
+                  if (_formKey.currentState!.validate()) {
+                    final newUser = User(
+                      id: 0, // API will assign the real ID
+                      name: _nameController.text,
+                      email: _emailController.text,
+                    );
+                    // Add user and return to previous screen
+                    await ref.read(usersProvider.notifier).addUser(newUser);
+                    popContext();
+                  }
+                },
+                child: const Text('Add User'),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

examples/rest_api/pubspec.yaml

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+name: rest_api
+description: "A demo for handling rest api with riverpod"
+publish_to: 'none' 
+version: 1.0.0+1
+
+environment:
+  sdk: '>=3.0.0 <4.0.0'
+dependencies:
+  flutter:
+    sdk: flutter
+  flutter_riverpod: ^2.6.1
+  dio: ^5.8.0
+
+  cupertino_icons: ^1.0.8
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+
+  flutter_lints: ^5.0.0
+  mockito: ^5.4.4
+  build_runner: ^2.4.8
+
+flutter:
+
+
+  uses-material-design: true