Underline in metauml

Question

\documentclass{article}
\usepackage[shellescape]{gmp}
\begin{document}
\begin{figure}
\begin{mpost}[use]
input metauml;

Class.A("A")
       ("-instance: A")
       ("-A()",
        "+instance(): A");

drawObjects(A);
\end{mpost}
\caption{Class \texttt{A} as a singleton}
\label{fig:uml-a}
\end{figure}
\end{document}

How can I make +instance(): A underlined to mark it as a static method?

Is it possible to disable converting + and - to graphics ?

Egreg's solution below works but is there any way to draw "true" underline? For example if I add something below underlined part I would have to move line maually. I want to avoid this.

Answer 1

You should use mpsettings={input metauml;}; then you can use Metapost for drawing a line.

\documentclass{article}
\usepackage[shellescape]{gmp}
\begin{document}
\begin{figure}
\begin{mpost}[use,mpsettings={input metauml;}]

Class.A("A")
       ("-instance: A")
       ("-A()",
        "+instance(): A");

drawObjects(A);

draw A.sw+(13,1.5) -- A.se+(-4,1.5);

\end{mpost}
\caption{Class \texttt{A} as a singleton}
\label{fig:uml-a}
\end{figure}
\end{document}

In order to change the + and - to something else than the default, one should study in detail the source metauml.mp

Answer 2

Idea in drawing line under "attribute" label. (reputation killed image)

+---------------------+
|      Singleton      |
+---------------------+
| -  static Instance  |
|   ----------------- |
+---------------------+
|                     |
+---------------------+

This is variation on egreg 's answer. It is possible that more accurate answer exist...

input metauml;

beginfig(1);
    Class.SingletonLite("Singleton")("- static Instance")();

    drawObject(SingletonLite);

    draw SingletonLite.attributeStack.pict[0].sw -- SingletonLite.attributeStack.pict[0].se ;
endfig;

end.

Answer 3

The following suggestions work with the code in the master branch of MetaUML, but not with MetaUML 0.2.5.

It is possible to explicitly mark class features as abstract or static:

metaUML class diagram: set some methods as abstract in an abstract class

Text can be underlined as follows:

Picture.a("foo");
a.info.textDecoration := "underline";

The use of locks as visibility markers has been discontinued in favour of the standard UML notation.