pgfooclass: passing a coordinate to the constructor or method

Question

In the stamp class example in the pgfmanual, the position for the stamp is passed in as two separate numbers, an x coordinate and a y coordinate. Is it possible, instead, to pass in a coordinate or a 'point' of some kind?

@percusse I have made some progress since I posted the question but it's not very elegant. I would welcome pointers on a better way to get the coordinates into the class.

\documentclass{article}
\usepackage{tikz}
\usepgfmodule{oo}
%http://tex.stackexchange.com/questions/33703/extract-x-y-coordinate-of-an-arbitrary-point-in-tikz
\makeatletter
\newcommand{\gettikzxy}[3]{%
    \tikz@scan@one@point\pgfutil@firstofone#1\relax
    \edef#2{\the\pgf@x}%
    \edef#3{\the\pgf@y}%
}
\makeatother

\pgfooclass{rr}{
  \method rr(#1,#2) { % The constructor; everything is done in here
    % This doesn't seem to work
    % \def\start{#1} % nor \def\start{(#1)}
    % But here I can get named x and y coordinates
    \gettikzxy{(#1)}{\spx}{\spy}
    \gettikzxy{(#2)}{\epx}{\epy}
    % I'd like named points to work with
    \coordinate (Start) at (\spx, \spy);
    \coordinate (End) at (\epx, \epy);
   \draw (Start) -- (End) node[right] {It works!};
  }
}

\begin{document}
\begin{tikzpicture}
    \coordinate (A) at (0,0);
    \coordinate (B) at (0,-1);
    \def\hi{0.25}
    \pgfoonew \AB=new rr(A,B);
    \fill (A) circle (3pt);
    \fill (B) circle (3pt);
\end{tikzpicture}
\end{document}

I am refactoring some code I wrote years ago. This is where I'm going:

Answer 1

The reason why the position is passed as two separate numbers is that the comma in \mystamp.apply(1,2) serve as the separator of parameters, not part of the coordinate.

You probably had already known that in the usual TikZ, it is inappropriate to write

\draw[shift=(3,4)](A)--(B);

simply because the comma serves as the separator of styling keys, and one should instead write

\draw[shift={(3,4)}](A)--(B);

Here the idea is the same: if you are willing to protect your parameters by braces, then you can pass almost everything: including but not limited to

• xy-coordinates (1,2)
• xyz-coordinates (3,4,5)
• polar coordinates (60:7)
• coordinate system (canvas cs:x=8,y=9)
• node and node-anchor (A.south east)
• calculations provided by calc library ($(A)+(B)!.5!(C)$)

Basically the dirty job is done by the underlying TikZ parser, and the oo part is merely syntactic sugar.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\usepgfmodule{oo}
\begin{document}

\pgfooclass{pen}{
    \method pen(){
        %
    }
    \method point(#1,#2,#3){ % position,name,color
        \path(#1)coordinate(#2)node[below right,text=#3]{$#2$};
    }
    \method segment(#1,#2,#3){ % start,end,color
        \draw(#1)circle(.1)(#2)circle(.1);
        \draw[#3](#1)--(#2);
    }
    \method ray(#1,#2,#3){ % start,end,color
        \draw(#1)circle(.1)(#2)circle(.1);
        \draw[#3,overlay,shorten >=-10000](#1)--(#2);
    }
    \method line(#1,#2,#3){ % start,end,color
        \draw(#1)circle(.1)(#2)circle(.1);
        \draw[#3,overlay,shorten <=-10000,shorten >=-10000](#1)--(#2);
    }
}
\pgfoonew \mypen=new pen()
\begin{tikzpicture}
    \draw[lightgray](-5,-5)grid(5,5);
    \draw[->](-6,0)--(6,0);
    \draw[->](0,-6)--(0,6);
    \mypen.point({3,3},A,violet)
    \mypen.point({current bounding box.200},B,olive)
    \mypen.point({0,-4},C,brown)
    \mypen.segment({-5,4},A,red)
    \mypen.ray(B,{40:2},blue)
    \mypen.line({$(A)+(0,-4)$},{$(C)!.5!(B)$},teal)
\end{tikzpicture}

\end{document}