Use TiKZ-graphdrawing with overlay specifications of beamer

Question

I would like to progressively develop a graph created with during a beamer presentation. Here is a MWE:

\documentclass{beamer}

\usepackage{tikz}

\usetikzlibrary{graphs, graphdrawing}
\usegdlibrary{layered}

\begin{document}
\begin{frame}
    \begin{tikzpicture}
        \graph[layered layout]
        {%
            "1" -- {"2", "3"},

            {"2", "3"}  -- "4",
            % \only<2->{{"2", "3"}  -- "4",}
            {"2", "3"} -- "5",
            % \only<3->{{"2", "3"} -- "5",}

            {"4", "5"} -- "6",
            % \only<4->{{"4", "5"} -- "6",}

        };
    \end{tikzpicture}
\end{frame}
\end{document}

The commented lines show my intent but they lead to errors.

Ty for any help.

Answer 1

You could use the overlay-beamer-styles library:

% !TeX TS-program = lualatex

\documentclass{beamer}

\usepackage{tikz}

\usetikzlibrary{graphs, graphdrawing}
\usegdlibrary{layered}
\usetikzlibrary{overlay-beamer-styles}

\begin{document}

\begin{frame}
    \begin{tikzpicture}
        \graph[layered layout]
        {%
            "1" -- {"2", "3"},

            {"2", "3"} -- [draw on=<2->] "\alt<2->{4}{\phantom{4}}",
            
            {"2", "3"} -- [draw on=<3->] "\alt<3->{5}{\phantom{5}}",
            
            {"\alt<2->{4}{\phantom{4}}", "\alt<3->{5}{\phantom{5}}"} -- [draw on=<4->] "\alt<4->{6}{\phantom{6}}",

        };
    \end{tikzpicture}
\end{frame}
\end{document}

Answer 2

samcarter already introduced the nice idea of using the overlay-beamer-styles library.

An alternative approach to their use of the \alt macro would be to use the visible on option provided by this library. It essentially sets the options opacity and text opacity to zero, which means that you won't get any layout shifts and you can even keep the node names. You would need to apply this option both to the edges and the nodes.

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{graphs, graphdrawing}
\usegdlibrary{layered}
\usetikzlibrary{overlay-beamer-styles}

\begin{document}
\begin{frame}
    \begin{tikzpicture}
        \graph[layered layout]
        {%
            "1" -- {"2", "3"},
            
            {"2", "3"} -- [visible on=<2->] "4" [visible on=<2->],

            {"2", "3"} -- [visible on=<3->] "5" [visible on=<3->],

            {"4", "5"} -- [visible on=<4->] "6" [visible on=<4->],
        };
    \end{tikzpicture}
\end{frame}

\end{document}