Error Handling with Dio in Flutter Apps

Learn how to implement robust error handling in Flutter applications using Dio HTTP client.

Discover best practices for handling network errors, timeouts, and creating custom error handlers.

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Error Handling with Dio in Flutter Applications

In the world of Flutter development, making HTTP requests is a fundamental part of building modern applications. While Dio is an excellent HTTP client for Flutter, proper error handling is crucial for creating robust and user-friendly apps. Let’s dive into how we can implement effective error handling with Dio.

Understanding Dio Errors

When working with Dio, we encounter different types of errors that need to be handled appropriately. These can range from network connectivity issues to server-side errors.

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try {
  final response = await dio.get('/api/data');
} on DioException catch (e) {
  if (e.type == DioExceptionType.connectionTimeout) {
    print('Connection timed out');
  } else if (e.type == DioExceptionType.connectionError) {
    print('No internet connection');
  }
}

Creating a Custom Error Handler

To maintain clean and reusable code, it’s recommended to create a dedicated error handler class that can manage different types of errors consistently across your application.

class DioErrorHandler {
  static String handleError(DioException error) {
    switch (error.type) {
      case DioExceptionType.connectionTimeout:
        return 'Connection timed out';
      case DioExceptionType.sendTimeout:
        return 'Request timed out';
      case DioExceptionType.connectionError:
        return 'No internet connection';
      case DioExceptionType.badResponse:
        return _handleBadResponse(error.response?.statusCode);
      default:
        return 'Something went wrong';
    }
  }

  static String _handleBadResponse(int? statusCode) {
    switch (statusCode) {
      case 400:
        return 'Bad request';
      case 401:
        return 'Unauthorized';
      case 404:
        return 'Not found';
      case 500:
        return 'Internal server error';
      default:
        return 'Server error';
    }
  }
}

Implementing Error Interceptors

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Dio provides powerful interceptor capabilities that allow us to handle errors globally. This is particularly useful for consistent error handling across your entire application.

dio.interceptors.add(
  InterceptorsWrapper(
    onError: (DioException error, handler) {
      // Log the error
      logger.e('API Error: ${error.message}');

      // Transform the error message
      final errorMessage = DioErrorHandler.handleError(error);

      // Show user-friendly message
      showErrorSnackBar(errorMessage);

      return handler.next(error);
    },
  ),
);

Best Practices for Error Handling

Always handle timeout scenarios
Implement retry mechanisms for failed requests
Show user-friendly error messages
Log errors for debugging purposes
Handle offline scenarios gracefully

Future\<T\> makeApiRequest\<T\>(Future\<T\> Function() request) async {
  try {
    return await request();
  } on DioException catch (e) {
    final errorMessage = DioErrorHandler.handleError(e);
    throw CustomException(errorMessage);
  } catch (e) {
    throw CustomException('An unexpected error occurred');
  }
}

By implementing proper error handling, your Flutter applications will become more resilient and provide a better user experience. Remember to always test your error handling implementation with different scenarios to ensure it works as expected.

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