# Setting a specific key (and value) depending on state of \if macro

This question is basically a follow-up of two older questions I posted a year ago, but actually is a consequence of trying to find a solution to this question:

Use toggles in biblatex printbibliography

I want to use a command with a key-value setup with an \if statement (pseudocode)

\somekeycommand[\ifdisplay somekey=A \else someotherkey=B]

such that some specific key is set according to the state of the variable \ifdisplay.

Unfortunately none of the various approaches work, not even the \begingroup\edef\x{\endgroup\noexpand....}\x - trick is successful.

Please note, that I don't want to use

\ifdisplay
\somekeycommand[somekey=A]
\else
\somekeycommand[someotherkey=B]
\fi


The actual \somekeycommand is some code from a package, the macro uses \setkeys

Here is the failing MWE

\documentclass{article}
\usepackage{etoolbox}
\usepackage{xparse}
\usepackage{xkeyval}

\makeatletter
\define@key{myfam}{somekey}{%
\def\somekeyvalue{#1}%
}

\define@key{myfam}{someotherkey}{%
\def\somekeyothervalue{#1}%
}

\makeatother

\NewDocumentCommand{\somekeycommand}{+O{}}{%
\begingroup
\setkeys{myfam}{#1}%
\ifdef{\somekeyvalue}{%
Key was \somekeyvalue%
}{%
}%
\endgroup
}%

\newif\ifdisplay
\displayfalse

\begin{document}

\somekeycommand[somekey=A]

\edef\x{%
\expandafter\noexpand\csname ifdisplay\endcsname%
somekey=A%
\noexpand\else%
someotherkey=B%
\noexpand\fi%
}%

\somekeycommand[\x] % fails

\somekeycommand\expandafter[\x] % fails --> expands to [ \expanded value ]

\somekeycommand[\expandafter\begingroup\edef\x{%
\ifdisplay
somekey=A%
\else%
someotherkey=B%
\fi%
}\x] %% -> fails, prints someotherkey=B,

\expandafter\somekeycommand[\begingroup\edef\x{%
\noexpand\ifdisplay
somekey=A%
\noexpand\else%
someotherkey=B%
\noexpand\fi%
}\x] %% -> fails, prints someotherkey=B,

\end{document}


Here are the older questions of mine:

• \setkeys doesn't expand its second argument. I don't really understand what you're after. – egreg Feb 15 '15 at 22:12
• @egreg: Isn't it possible at all? I wonder if it's possible to set either keyA or keyB (the key-value itself is irrelevant for now) depending whether \ifdisplay is evaluated to be true or to be false. The keys are different – user31729 Feb 15 '15 at 22:22

## 1 Answer

Note that \setkeys doesn't expand its second argument. I'm not sure what you're after, but this works.

\documentclass{article}
\usepackage{etoolbox}
\usepackage{xparse}
\usepackage{xkeyval}

\makeatletter
\define@key{myfam}{somekey}{%
\def\somekeyvalue{#1}%
}

\define@key{myfam}{someotherkey}{%
\def\somekeyothervalue{#1}%
}

\makeatother

\NewDocumentCommand{\somekeycommand}{+O{}}{%
\begingroup
\setkeys{myfam}{#1}%
\ifdef{\somekeyvalue}
{Key was \somekeyvalue}
{\ifdef{\somekeyothervalue}{Other key was \somekeyothervalue}{}}%
\endgroup
}%

\newif\ifdisplay
\displayfalse

\begin{document}

\begingroup\edef\x{\endgroup\noexpand
\somekeycommand\expandafter[\ifdisplay somekey=A\else someotherkey=B\fi]%
}\x

\displaytrue

\begingroup\edef\x{\endgroup\noexpand
\somekeycommand\expandafter[\ifdisplay somekey=A\else someotherkey=B\fi]%
}\x

\end{document}


• I think this is what I want to achieve. And I had something similar, but it failed with some complains about \endgroup. – user31729 Feb 15 '15 at 22:27
• Could you answer tex.stackexchange.com/questions/228293/… too? ;-) – user31729 Feb 15 '15 at 22:29