Use pgfkeys to set a style variable

Question

I'd like to use pgfkeys to define the scale for a number of tikz pictures. However, wenn I do the following:

\documentclass{article}
\usepackage{tikz}
\begin{document}
    \pgfkeys{/my special/variable/.code={.1}}
    \begin{tikzpicture}[scale={/my special/variable}]
        \draw (0,0) -- (1,1);
    \end{tikzpicture}
\end{document}

I get: Package PGF Math Error: Unknown function 'my' (in '/my special/variable').

... [scale = \pgfkeys{/my special/variable}] ... does not work, either. LaTeX complains: TeX capacity exceeded, sorry.

What's the right way to define a variable that can be used to set a style or other variable in TikZ?

Answer 1

Try some thing like

\documentclass{article}
\usepackage{tikz}
\pgfkeys{/tikz/.cd,
  myvar/.store in=\myvar,
  myvar=0.1,
   }
\begin{document}
    \begin{tikzpicture}[myvar=2,scale={\myvar}]
        \draw (0,0) -- (1,1);
    \end{tikzpicture}
\end{document}

If you don't give myvar=2,, the intial value (0.1) is used.