getExternalUrl example

if (!$scheme) {
      $baseUrl = $relative ? base_path() : $this->requestStack->getCurrentRequest()->getSchemeAndHttpHost() . base_path();
      return $this->generatePath($baseUrl, $uri);
    }
    elseif ($scheme == 'http' || $scheme == 'https' || $scheme == 'data') {
      // Check for HTTP and data URI-encoded URLs so that we don't have to       // implement getExternalUrl() for the HTTP and data schemes.       return $relative ? $this->transformRelative($uri) : $uri;
    }
    elseif ($wrapper = $this->streamWrapperManager->getViaUri($uri)) {
      // Attempt to return an external URL using the appropriate wrapper.       $externalUrl = $wrapper->getExternalUrl();
      return $relative ? $this->transformRelative($externalUrl) : $externalUrl;
    }
    throw new InvalidStreamWrapperException();
  }

  /** * Generate a URL path. * * @param string $base_url * The base URL. * @param string $uri * The URI. * * @return string * The URL path. */