How to pass figure position to keyval macro?

Question

I want to wrap a macro around figure-env to make my document more readable. Here is minimal example of how it is now:

\documentclass[10pt,a4paper]{article}
\usepackage{keyval}

\makeatletter

\define@key{image}{pos}{\def\i@pos{#1}} % define key-val
\setkeys{image}{pos=!htbp} % set default
\newcommand{\image}[2][]{%
  \begingroup%
  \setkeys{image}{#1}% set passed key-vals
  \begin{figure}[\i@pos] % use positon
    \centerline{\includegraphics[width=\textwidth]{#2}}
  \end{figure}
  \endgroup%}

\makeatother
\begin{document}
\end{document}

but it seems that the default position !htbp is not set, because if i set it directly in \begin{figure}[!htbp] it works perfectly fine and the images are positioned correctly.

Edit: I added \begin{document} and \end{document} as suggested in the comments to make it compileable.

I appreciate you help.

Answer 1

\begin{figure} doesn't expand the optional argument; when expansion happens it's too late.

\documentclass[10pt,a4paper]{article}
\usepackage{keyval}
\usepackage[demo]{graphicx}% draft is just for the example

\makeatletter

\define@key{image}{pos}{\def\i@pos{#1}} % define key-val
\setkeys{image}{pos=!htbp} % set default
\newcommand{\image}[2][]{%
  \begingroup
  \setkeys{image}{#1}% set passed key-vals
  \def\@temp{\begin{figure}}%
  \expandafter\@temp\expandafter[\i@pos]% use position
  \centering
  \includegraphics[width=\textwidth]{#2}
  \end{figure}
  \endgroup}

\makeatother

\begin{document}
Some text

\image[pos=!htbp]{foo}

Some other text
\end{document}

Alternatively, since the value given to pos is formed by unexpandable tokens,

\newcommand{\image}[2][]{%
  \begingroup
  \setkeys{image}{#1}% set passed key-vals
  \begingroup\edef\x{\endgroup
    \noexpand\begin{figure}[\i@pos]}\x % use position
  \centering
  \includegraphics[width=\textwidth]{#2}
  \end{figure}
  \endgroup}