The defined command not work in \ifdefined

Question

Why this MWE doesn't work?

\begin{filecontents*}[overwrite]{myClass.cls}
\NeedsTeXFormat{LaTeX2e}
\ProvidesClass{myClass}
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{article}}
\ProcessOptions\relax
\LoadClass{article}
\def\fullname#1{\gdef\@fullname{#1}}
%
\ifdefined\@fullname
\def\myTable{%
    \begin{tabular}{ll}
    Some & Text\\
    \@fullname & Text
    \end{tabular}%
}
\else
    \def\myTable{Why not defined?!}
\fi
\end{filecontents*}
\documentclass{myClass}
\begin{document}
    \fullname{Defined}
    \myTable
\end{document}

Because you are testing the defined at the time the class is loaded, not when the code is executed. — Steven B. Segletes, May 03 '21 at 14:53

Steven B. Segletes · Accepted Answer · 2021-05-03T15:09:43.263

3

As the OP structured it, the \ifdefined test was being performed as the class was loading. Instead, it should be performed during the document phase. I do that here by including the test in the definition of \myTable.

EDIT: I also changed the \else condition of \MyTable to actually print out the "warning", rather than merely to define it.

\begin{filecontents*}[overwrite]{myClass.cls}
\NeedsTeXFormat{LaTeX2e}
\ProvidesClass{myClass}
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{article}}
\ProcessOptions\relax
\LoadClass{article}
\def\fullname#1{\gdef\@fullname{#1}}
%
\newcommand\myTable{%
 \ifdefined\@fullname
    \begin{tabular}{ll}
    Some & Text\\
    \@fullname & Text
    \end{tabular}%
 \else
    Why not defined?!
 \fi
}
\end{filecontents*}
\documentclass{myClass}
\begin{document}
    \fullname{Defined}
    \myTable
\end{document}

edited May 03 '21 at 15:09

answered May 03 '21 at 14:53

Steven B. Segletes

237,551

1

This time I'm the one beaten by a few seconds... :-) – campa May 03 '21 at 14:54
@campa Maybe for today, but I'm sure the roles will soon reverse and you can again be the fastest \draw in the .west. – Steven B. Segletes May 03 '21 at 14:59
Thank you, but now when I comment the \fullname{Defined}, doesn't work again. – Bahman Mirzakhani May 03 '21 at 15:01
1

@BahmanMirzakhani I see that in the \else condition of \myTable you only redefined \MyTable for a future use (and did not print out anything!). I have changed the answer to actually print out "Why not defined?" Perhaps this is easier to understand. – Steven B. Segletes May 03 '21 at 15:11

The defined command not work in \ifdefined

1 Answers1