now it works but it was necessary to add even an
#include <cstdlib>
that has the taste of C. Now I'm not sure if atoi() can work with String or at some moment the application will crash. I've ALT+J in String.cpp to understand if AsString return a C string of something else. The result of the investigation was a nightmare .
The question: does exist a smart U++ way to produce the correct cast or what I have done is enough?