Use of \foreach and \csname<macro name>\endcsname together

Question

When I compile this minimum LaTeX file:

\documentclass{report}

\def\defMacro#1#2{\expandafter\def\csname#1\endcsname{#2}}
\def\useMacro#1{\csname#1\endcsname}

\usepackage{pgffor}

\begin{document}
\foreach \n in {0,1,...,10}{
\defMacro{number:\n}{\n}
}


\useMacro{number:8}
\end{document}

I obtain no PDF output. What do I mistake?

Answer 1

The \foreach loop content is executed in a group for each iteration, therefore the definition is only local. You would need to add \global in front of \defMacro.

The reason the \useMacro is not causing an error is because \csname has the side effect that the resulting macro is defined equal to \relax if is was undefined before.