Generic Request

base_service.dart

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

abstract class BaseService {
  static const String baseUrl = 'http://some-supercool-api-address:s0m3-p0rt';
  final String endpoint;
  late final Map<String, dynamic> response;

  BaseService({required this.endpoint});

  Future<T> request<T>(
    String method, {
    Map<String, dynamic>? body,
    Map<String, String>? headers,
  }) async {
    final String url = '$baseUrl/$endpoint';
    final Uri uri = Uri.parse(url);

    try {
      late http.Response response;

      final Map<String, String> defaultHeaders = {
        'Content-Type': 'application/json',
        ...?headers,
      };

      switch (method.toUpperCase()) {
        case 'GET':
          response = await http.get(uri, headers: defaultHeaders);
          break;
        case 'POST':
          response = await http.post(
            uri,
            headers: defaultHeaders,
            body: jsonEncode(body),
          );
          break;
        case 'PUT':
          response = await http.put(
            uri,
            headers: defaultHeaders,
            body: jsonEncode(body),
          );
          break;
        case 'DELETE':
          response = await http.delete(uri, headers: defaultHeaders);
          break;
        default:
          throw Exception('Método HTTP não suportado: $method');
      }

      if (response.statusCode >= 200 && response.statusCode < 300) {
        return json.decode(response.body) as T;
      } else {
        throw Exception('Erro ${response.statusCode}: ${response.body}');
      }
    } catch (error) {
      throw Exception('Erro na requisição: $error');
    }
  }
}

// Then require like this
Future<List<MyModel>> all() async {
  final List<dynamic> response = await request<List<dynamic>>('GET');

  return response.map((model) => MyModel.fromJson(model)).toList();
}