How to create a common class in Flutter for managing GET and POST requests using the http package?

Add http dependency to pubspec.yaml

dependencies:
  http: ^0.13.6

2. Create a file: api_service.dart

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

class ApiService {
  final String baseUrl;

  ApiService({required this.baseUrl});

  Future<dynamic> get(String endpoint, {Map<String, String>? headers}) async {
    final url = Uri.parse('$baseUrl$endpoint');
    try {
      final response = await http.get(url, headers: headers);
      return _handleResponse(response);
    } catch (e) {
      throw Exception('GET request error: $e');
    }
  }

  Future<dynamic> post(String endpoint, {Map<String, String>? headers, dynamic body}) async {
    final url = Uri.parse('$baseUrl$endpoint');
    try {
      final response = await http.post(
        url,
        headers: headers ?? {'Content-Type': 'application/json'},
        body: json.encode(body),
      );
      return _handleResponse(response);
    } catch (e) {
      throw Exception('POST request error: $e');
    }
  }

  dynamic _handleResponse(http.Response response) {
    final statusCode = response.statusCode;
    final body = response.body.isNotEmpty ? json.decode(response.body) : null;

    if (statusCode >= 200 && statusCode < 300) {
      return body;
    } else {
      throw Exception('Error ${response.statusCode}: ${response.reasonPhrase}');
    }
  }
}

3. Usage Example:

void main() async {
  final api = ApiService(baseUrl: 'https://jsonplaceholder.typicode.com/');

  // GET request
  try {
    final posts = await api.get('posts');
    print(posts);
  } catch (e) {
    print(e);
  }

  // POST request
  try {
    final newPost = await api.post('posts', body: {
      'title': 'foo',
      'body': 'bar',
      'userId': 1,
    });
    print(newPost);
  } catch (e) {
    print(e);
  }
}