Non-intersecting lines on class diagram

Question

\documentclass{article}
\usepackage[shellescape]{gmp}
\begin{document}

\begin{mpost}[use,mpsettings={input metauml;}]
Class.A("A")()();
Class.B("B")()();
Class.C("C")()();
Class.D("D")()();

B.n = A.s + (0,-80);
C.w = D.w + (-80,0);
A.s = C.w + (50,40);
drawObjects(A, B, C, D);
clink(association)(A,B);
clink(association)(C,D);
\end{mpost}
\end{document}

The ouput I get:

As you can see lines A--B and C--D intersect.

I really need something like this:

How can I do that?

Answer 1

Take a look at section 8 and especially subsection 8.5 of the metauml manual.

Code

\documentclass{article}
\usepackage[shellescape]{gmp}
\begin{document}

\begin{mpost}[use,mpsettings={input metauml;}]
Class.A("A")()();
Class.B("B")()();
Class.C("C")()();
Class.D("D")()();

B.n = A.s + (0,-80);
C.w = D.w + (-80,0);
A.s = C.w + (50,40);
drawObjects(A, B, C, D);
clink(association)(A,B);
%clink(association)(C,D);
path cool;
cool := C.e -- C.c+(38,0) .. C.c+(40,2) .. D.c+(-38,0) -- D.w;
link(association)(cool);
\end{mpost}
\end{document}

Output