我想从文件中加载数据并将其用于图片标题。我有一个在某些环境下有效的解决方案

Question

我想从文件加载数据并将其用于图片标题。找到这代码（我稍作修改以展示它的局限性）在工作时完全符合我的要求，例如在数学环境中。但它在图形标题或章节标题中根本不起作用。有什么办法可以解决这个问题吗？

    \documentclass{article}
    \usepackage{datatool, filecontents}
    \DTLsetseparator{ = }

    \begin{filecontents*}{mydata.dat}
    foo = 10
    bar = 20
    \end{filecontents*}

    \begin{document}
    \DTLloaddb[noheader, keys={thekey,thevalue}]{mydata}{mydata.dat}
    \newcommand{\mycommand}[1]{\DTLfetch{mydata}{thekey}{#1}{thevalue}}

    %This works
    The first value \mycommand{foo} and the second value $\mycommand{bar}$.

    %This doesn't
    \section{\mycommand{foo}}

    %Nor this
    \begin{figure}
        \caption{And some parameter has the value \mycommand{foo}}
    \end{figure}
    \end{document}

Answer 1

\protect\mycommand定义的命令很脆弱，因此在移动参数（例如\section或 ）中使用时需要使用\caption。

Answer 2

readarray/方法listofitems效果很好。

\documentclass{article}
\usepackage{readarray}

\begin{filecontents*}{mydata.dat}
foo = 10
bar = 20
\end{filecontents*}

\newcommand\mycommand[1]{\csname keydata#1\endcsname}
\begin{document}
\readarraysepchar{;}
\readdef{mydata.dat}\mydata
\setsepchar{;/=}
\ignoreemptyitems
\readlist*\myrecords{\mydata}
\foreachitem\z\in\myrecords[]{%
  \expandafter\xdef\csname keydata\myrecords[\zcnt,1]\endcsname{%
    \myrecords[\zcnt,2]}%
}
%This works
The first value \mycommand{foo} and the second value $\mycommand{bar}$.
%This doesn't
\section{\mycommand{foo}}
%Nor this
\begin{figure}
\caption{And some parameter has the value \mycommand{foo}}
\end{figure}
\end{document}

如果您需要保留未扩展的关键数据，只需稍微努力一下就可以得到以下结果：

\documentclass{article}
\usepackage{readarray}
\usepackage[T1]{fontenc}
\begin{filecontents*}{mydata.dat}
foo = 10
bar = 20
foomac = \today
\end{filecontents*}

\newcommand\mycommand[1]{\csname keydata#1\endcsname}
\begin{document}
\readarraysepchar{;}
\readdef{mydata.dat}\mydata
\setsepchar{;/=}
\ignoreemptyitems
\readlist*\myrecords{\mydata}
\foreachitem\z\in\myrecords[]{%
  \expandafter\def\csname keydata\myrecords[\zcnt,1]\expandafter\expandafter
  \expandafter\endcsname\expandafter\expandafter\expandafter{%
  \myrecords[\zcnt,2]}%
}
%This works
The first value \mycommand{foo} and the second value $\mycommand{bar}$.

Key value3 is not pre-expanded: 
\detokenize\expandafter{\keydatafoomac}.
%This doesn't
\section{\mycommand{foo}}
%Nor this
\begin{figure}
\caption{And some parameter has the value \mycommand{foo}}
\end{figure}
\end{document}