pgfkey containing a foreach statement with a variable number of values

Question

I would like to use pgfkeys in a macro. One key contains a foreach statement which handles a variable number of values. I have some problems concerning the right order of the output. Here a simplified example:

\documentclass[article]{memoir}
\usepackage[latin]{babel}
\usepackage{algpseudocode}
\usepackage{pgfkeys}

\pgfkeys{%
/test/.is family,
/test/.cd,
    key a/.store in = \keyA,
    key a print/.code = \texttt{\keyA},
    key b/.code = {\foreach \x in {#1}{\textbf{\x}--}}
}%

\newcommand\mymacro[1]{\pgfkeys{/test, #1, key a print}}

\begin{document}
\mymacro{key a = valueKeyA, key b = {valueKeyB1, valueKeyB2, valueKeyB3}}
\end{document}

The order of the output is: valueKeyB1–valueKeyB2–valueKeyB3–valueKeyA

How can I achieve that valueKeyA is typeset first? If I put #1 at the end of the key list in my example code I get an error message. If I place it at the end of the key list in my actual code the values of the first keys are missing. I guess it has either something to do with the order in which the values are stored and the keys are executed or my use of #1 is mixed up.

I am using pgfkeys for a short time and would be glad if someone could give me a hint.

Answer 1

At the moment, the keys are executed in the following order:

1. key a = valueKeyA. This stores valueKeyA in the macro \keyA.
2. key b = {valueKeyB1, valueKeyB2, valueKeyB3}. This prints out valueKeyB1--valueKeyB2--valueKeyB3-- (ignoring formatting)
3. key a print. This prints out \keyA which expands to valueKeyA.

So the problem is that for key a, the processing is split into two parts: storing and printing, whilst for key b this is all done in one step. The order in which you call things means that the two steps for a are split by the one step for b. There are a variety of ways to fix this depending on what you want to achieve.

Before giving some, let me explain why putting #1 at the end doesn't work. This is because that puts step 3 above first, whereupon it tries to print out the value of \keyA which hasn't been set yet.

As I said, how to fix this depends on what you want to do in your real code. Here are a couple.

1. Put the key a print inside the argument to \mymacro in the right place, so we have:

   \newcommand\mymacro[1]{\pgfkeys{/test, #1}}
   
   \begin{document}
   \mymacro{key a = valueKeyA, key a print, key b = {valueKeyB1, valueKeyB2, valueKeyB3}}
   

2. Make the key a step both store and print its value, something like:

   \pgfkeys{/test/.cd, key a/.code={\def\keyA{#1}\texttt{#1}}}
   

   Then remove key a print from everywhere.

3. Make the key b step store its result in a macro to be printed out later. Something like:

   \pgfkeys{/test/.cd, key b/.code={\def\keyB{}\foreach \x in {#1}{\expandafter\gdef\expandafter\keyB\expandafter{\keyB\textbf{\x}--}}}, key b print/.code={\keyB}}
   

   Then add key b print after key a print (or do a combined print all keys).

There are probably more - even if those don't prove to be useful they should help you figure out what features of a solution you would like.