What is the syntax to get QNetworkReply::HostNotFoundError back from QNetworkReply?

First I generate a QNetworkReply like this:

Qt Code: 
  1. QNetworkAccessManager* nam = new QNetworkAccessManager(this);
  2. QNetworkReply* reply = nam->get(QNetworkRequest(url));
To copy to clipboard, switch view to plain text mode 

Then I know how to get QNetworkRequest::HttpStatusCodeAttribute from this QNetworkReply:

Qt Code: 
  1. QVariant statusCodeV = reply->attribute(QNetworkRequest::HttpStatusCodeAttribute);
To copy to clipboard, switch view to plain text mode 

How do I get QNetworkReply error in a similar fashion?? The prototype is here
Qt Code: 
  1. enum QNetworkReply::NetworkError
To copy to clipboard, switch view to plain text mode 
but I don't know how to use such prototype. What is the syntax. Thanks a lot for your help!