onError method

@override void onError(DioError err, ErrorInterceptorHandler handler)

The callback will be executed on error.

If you want to continue the error , call handler.next.

If you want to complete the response with some custom data directly, you can resolve a Response object with handler.resolve and other error interceptor(s) will be skipped.

If you want to complete the response with an error message directly, you can reject a DioError object with handler.reject, and other error interceptor(s) will be skipped.

Implementation

@override
void onError(
  DioError err,
  ErrorInterceptorHandler handler,
) {
  if (err.response != null) {
    if ([301, 302].contains(err.response!.statusCode)) {
      final redirectCount = (err.requestOptions
              .extra['domainFrontingRawOptionsRedirectCount'] ??
          0);
      final location =
          err.response?.headers[HttpHeaders.locationHeader]?.first;
      if (location != null) {
        if (redirectCount <= 5) {
          final uri = err.requestOptions.uri.resolve(location);
          final request = err.requestOptions;

          final newRequest = request.copyWith(path: uri.path, extra: {
            ...request.extra,
            'domainFrontingRawOptionsRedirectCount': redirectCount + 1,
          });
          dio.fetch(newRequest).then((value) => handler.resolve(value));
          return;
        }
      }
    }
  }

  handler.next(err);
}