How do you define a command for use in a tikzpicture environment?

Question

I want to define an environment for the tikzpicture environment which defines tikz specific commands.

Here's an abbreviated example for a UML environment which defines a \Class command):

\newenvironment{UMLDiagram}{%
    \newcommand{\Class}[3]{\node[class](##1){##2\nodepart{second}{##3}};}%
    \begin{tikzpicture}[%
        class/.style={draw, rectangle split, rectangle split parts=2, align=left}%
    ]%
}{%
    \end{tikzpicture}%
}

I wanted to use this the following way:

\begin{UMLDiagram}
    \Class{id}{ClassName}{attributeA=a\\attributeB=b}
\end{UMLDiagram}

This---not entirely unexpected---throws an error:

! Undefined control sequence tizk@invoke@collected@onpath ...mmand \tikz@temp \pgf@stop (...)

However, a command with a single argument did not fail.

So, how do you do this? Or, on a related note, does tikz provide a mechanism for tikz specific command definitions?

MWE

\documentclass{minimal}

\usepackage{tikz}
\usetikzlibrary{shapes}

\newenvironment{UMLDiagram}{%
    \newcommand{\Class}[3]{\node[class](##1){##2\nodepart{second}{##3}};}%
    \begin{tikzpicture}[%
        class/.style={draw, rectangle split, rectangle split parts=2, align=left}%
    ]%
}{%
    \end{tikzpicture}%
}

\begin{document}

\begin{UMLDiagram}
    \Class{id}{ClassName}{attributeA=a\\attributeB=b}
\end{UMLDiagram}

\end{document}

Follow Up

The solution that worked for me was the use of a tabular environment within the node label as provided here.

    \newenvironment{UMLDiagram}{%
    \newcommand{\Class}[3]{
        \node[class](##1){%
            ##2%
            \nodepart{second}%
            \begin{tabular}{l}##3\end{tabular}%
        };
    }%
    \begin{tikzpicture}[%
        class/.style={draw, rectangle split, rectangle split parts=2, align=left}%
    ]%
}{%
    \end{tikzpicture}%
}

The align=left and \\ pattern would have been favorable but it did not work in this case.

score 4 · Accepted Answer · answered Jul 07 '14 at 10:25

The \\ is the reason for the error, if you remove it, your code succeed:

\documentclass{minimal}

\usepackage{tikz}
\usetikzlibrary{shapes}

\newenvironment{UMLDiagramm}{%
    \newcommand{\Class}[3]{\node[class](##1){\underline{##2}\nodepart{second}{##3}};}%
    \begin{tikzpicture}[%
        class/.style={draw, rectangle split, rectangle split parts=2, align=left}%
    ]%
}{%
    \end{tikzpicture}%
}

\begin{document}

\begin{UMLDiagramm}
    \Class{id}{ClassName}{attributeA=a,attributeB=b}% <=== replaced \\ with ,
\end{UMLDiagramm}

\end{document}

If you define a text width, you can use a newline command:

\documentclass{minimal}

\usepackage{tikz}
\usetikzlibrary{shapes}

\newenvironment{UMLDiagramm}{%
    \newcommand{\Class}[3]{\node[class](##1){\underline{##2}\nodepart{second}{##3}};}%
    \begin{tikzpicture}[%
        class/.style={draw, rectangle split, rectangle split parts=2, align=left,
        text width=3cm% <=== added
        }%
    ]%
}{%
    \end{tikzpicture}%
}

\begin{document}

\begin{UMLDiagramm}
    \Class{id}{ClassName}{attributeA=a\\attributeB=b}
\end{UMLDiagramm}

\end{document}

Ah, I see. Do you know any way to force the line break for an arbitrary width? — FK82, Jul 07 '14 at 10:56
Perhaps you find the solution in other questions: http://tex.stackexchange.com/questions/24372/how-to-add-newline-within-node-using-tikz — knut, Jul 07 '14 at 18:37
Not in those answers as far as I can see. What I want is \Class{id}{Name}{attributeA=a\\attributeB=b} without any width workarounds. — FK82, Jul 08 '14 at 09:03

How do you define a command for use in a tikzpicture environment?

1 Answers1