الگوی Singleton در Flutter: یک راهنمای جامع با نمونه های API

flutter:
sdk: flutter http: ^0.15.0

import 'package:http/http.dart' as http;
import 'dart:convert';

class ApiService {
// Private constructor ApiService._internal();

// Static instance of the class
static final ApiService _instance = ApiService._internal();

// Factory constructor to provide the instance factory ApiService() {
return _instance;
}

// Base URL of the API
static const String _baseUrl="https://jsonplaceholder.typicode.com";

// HTTP client
final http.Client _client = http.Client();

// GET request
Future get(String endpoint) async {
final response = await _client.get(Uri.parse('$_baseUrl/$endpoint')); return _handleResponse(response);
}

// POST request
Future post(String endpoint, dynamic body) async { final response = await _client.post(

Uri.parse('$_baseUrl/$endpoint'),
headers: {'Content-Type': 'application/json'}, body: jsonEncode(body),
);
return _handleResponse(response);
}

// PUT request
Future put(String endpoint, dynamic body) async { final response = await _client.put( Uri.parse('$_baseUrl/$endpoint'),
headers: {'Content-Type': 'application/json'}, body: jsonEncode(body),
);
return _handleResponse(response);
}

// PATCH request
Future patch(String endpoint, dynamic body) async { final response = await _client.patch( Uri.parse('$_baseUrl/$endpoint'),
headers: {'Content-Type': 'application/json'}, body: jsonEncode(body),
);
return _handleResponse(response);
}

// DELETE request
Future delete(String endpoint) async {
final response = await _client.delete(Uri.parse('$_baseUrl/$endpoint')); return _handleResponse(response);
}

// Handle the HTTP response
dynamic _handleResponse(http.Response response) { if (response.statusCode == 200) {
return jsonDecode(response.body);
} else {
throw Exception('Failed to load data: ${response.statusCode}');
}

}
}

class HomePage extends StatelessWidget {
final ApiService _apiService = ApiService();

Future fetchData() async { try {
final data = await _apiService.get('posts/1'); print('Fetched Data: $data');
} catch (e) { print('Error: $e');
}
}

@override
Widget build(BuildContext context) { return Scaffold(
appBar: AppBar(title: Text('Singleton Pattern Example')), body: Center(
child: ElevatedButton( onPressed: fetchData, child: Text('Fetch Data'),
),
),
);
}
}

Future createPost() async {
final newPost = { 'title': 'New Post',

'body': 'This is a new post created using the Singleton Pattern.', 'userId': 1,
};

try {
final response = await _apiService.post('posts', newPost); print('Created Post: $response');
} catch (e) { print('Error: $e');
}
}

Future updatePost() async {
final updatedPost = { 'id': 1,
'title': 'Updated Post',
'body': 'This post has been updated using the Singleton Pattern.', 'userId': 1,
};

try {
final response = await _apiService.put('posts/1', updatedPost); print('Updated Post: $response');
} catch (e) { print('Error: $e');
}
}

Future patchPost() async {
final patchData = { 'title': 'Patched Post',
};

try {
final response = await _apiService.patch('posts/1', patchData); print('Patched Post: $response');

} catch (e) { print('Error: $e');
}
}

Future patchPost() async {
final patchData = { 'title': 'Patched Post',
};

try {
final response = await _apiService.patch('posts/1', patchData); print('Patched Post: $response');
} catch (e) { print('Error: $e');
}
}

Request) Future deletePost() async {
try {
final response = await _apiService.delete('posts/1'); print('Deleted Post: $response');
} catch (e) { print('Error: $e');
}
}