How do I use the output of a macro to get multiple arguments for another macro?

Question

The following is my MWE:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{etoolbox}

\newcommand{\test}[1]{%
\ifstrequal{#1}{bla}{{blu1}{blu2}}{{error}{schmerror}}
}

\newcommand{\switch}[2]{#2 #1}

\begin{document}

\test{bla} % this works

\switch12 % this works

\switch\test{bla} \\

\expandafter\switch\test{bla}

\expandafter\switch\expandafter{\test{bla}}

\switch{\test{bla}}

\end{document}

This is the output:

I'm trying to get the \switch macro to take the output of \test{bla} as argument, returning blu2 blu2. But not even \expendafter does the trick. Is there any way to get something like this to work?

The first two lines just make sure that both commands work as expected.

My first attempt, \switch\text{bla}, obviously swaps \test and {bla} resulting in bla errorschmerror since the argument of \test isn't bla. (I think it's the \par token, since the next attempt outputs on the same line if I leave out \\.)

My second attempt, \expandafter\switch\test{bla}, just returns bla. As far as I can tell, \test simply gets replaced by nothing on expansion, and \switch switches {bla} with something (no idea what though). At first I wondered whether this was due to \ifstrequal not being expandable, which might somehow result in \test expanding to , but then the next attempt should show the same behavior.

However, my third attempt obviously does replace \test{bla} with {blu1blu2} on expansion. This then gets switched with something by \switch. This isn't what I intend though, I want \switchto operate on two arguments, {blu1} and {blu2}, which should both be provided by \test.

The fourth attempt seems to do exactly the same thing.

Answer 1

\expandafter\switch\test{bla}

is

\switch\ifstrequal{blah}{bla}{{blu1}{blu2}}{{error}{schmerror}}

which is

blah \ifstrequal {bla}{{blu1}{blu2}}{{error}{schmerror}}

which is not what you want.

You could change the call structure to

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{etoolbox}

\newcommand{\test}[2]{%
\ifstrequal{#2}{bla}{#1{blu1}{blu2}}{#1{error}{schmerror}}%
}

\newcommand{\switch}[2]{#2 #1}

\begin{document}

\test{}{bla}

\test\switch{bla} 

\end{document}