Edit `\@title` in the document

Question

I am using one info.tex file that contains title, author names etc:

\author{my name}
\title{my title}
\date{\today}

I read this file in other files:

\documentclass{article}
\input{info}
\begin{document}
    \maketitle
\end{document}

Now I have another file which has same author names etc., but the title is slightly different: With the previous title, I have to add "part II" (as if, \title{my title part II}). Instead of rewriting the title again (as I have may files like this), I want to edit the title name from this document.

I tried

\makeatlettezr
\let\newtitle\@title
\makeatother
\renewcommand{\newtitle}{\@title part II}
\makeatletter
\renewcommand{\@title}{\newtitle}
\makeatother

but, as you expected, I got error. Can anyone help?

Answer 1

You can redefine it using an \edef which expands the definition as much as possible. So you could do the following:

\makeatletter
\edef\@title{\@title\ part II}
\makeatother

If your \title does contain macros which shouldn't be expanded (yet) you can set things up so that \@title will be expanded only once with \unexpanded\expandafter:

\makeatletter
\edef\@title{\unexpanded\expandafter{\@title\ part II}}
\makeatother

In this case only the first token after the brace (so \@title in this case) will be expanded once.