LaTeX counters in TikZ foreach-loop with beamer

Question

I want to draw a complete graph with tikZ. At first the nodes, then the lines of the first node to the others, then the lines of the second node to the remaining and so forth. All these steps work with foreach-loops and each single drawing should appear step-by-step with the beamer function \visible<..>. My idea was to use a global LaTeX-counter to count all steps over all foreach-loops.

\documentclass[10pt,ngerman]{beamer}
\usepackage{tikz}
\newcounter{steps}
\begin{document}

\begin{frame}{Complete Graph}
    \begin{tikzpicture}[
        kreis/.style={circle, draw, minimum size=1.5cm},
        ]

        \foreach [count=\i] \letter in {A,...,F}{%
%           \stepcounter{steps}
            \visible<\thesteps->{%
                \node [kreis] (\letter) at (\i*60+30:2.5) {\huge{\letter}};
                }
            }
           \end{tikzpicture}
    \end{frame}
\end{document}

The MWE compiles, but when I remove the comment, then texmaker runs in an endless loop. Why?

Answer 1

You always increase the counter to a value that one more slide gets inserted because the slide gets "executed" several times. The beamer class has a command for such situations, \resetcounteronoverlays. Using this command fixes your problem.

\documentclass[10pt,ngerman]{beamer}
\usepackage{tikz}
\newcounter{steps}
\resetcounteronoverlays{steps}
\begin{document}

\begin{frame}{Complete Graph}
    \begin{tikzpicture}[
        kreis/.style={circle, draw, minimum size=1.5cm},
        ]

        \foreach [count=\i] \letter in {A,...,F}{%
           \stepcounter{steps}
            \visible<\thesteps->{%
                \node [kreis] (\letter) at (\i*60+30:2.5) {\huge{\letter}};
                }
            }
           \end{tikzpicture}
    \end{frame}
\end{document}

However, I would draw this differently anyway.

\documentclass[10pt,ngerman]{beamer}
\usepackage{tikz}
\usetikzlibrary{overlay-beamer-styles}
\begin{document}

\begin{frame}{Complete Graph}
    \begin{tikzpicture}[
        kreis/.style={circle, draw, minimum size=1.5cm},
        ]

        \foreach [count=\i] \letter in {A,...,F}{%
           {%
               \node[visible on=<\i->] [kreis] (\letter) at (\i*60+30:2.5) {\huge{\letter}};
                }
            }
     \end{tikzpicture}
\end{frame}
\end{document}