beamer definition-list overlay: uncover definition later than entry

Question

For educational purposes, I would like to uncover the definitions of my description items only after all the items themselves have been uncovered, like so:

\documentclass{beamer}
\begin{document}
\begin{frame}
\begin{overprint}
\begin{description}
\item<1->[Spam]
\onslide<3->{Eggs}
\item<2->[Cheese]
\onslide<4->{Tofu}
\end{description}
\end{overprint}
\end{frame}
\end{document}

However, this has the effect that both Spam and Eggs appear only on slide 3. I would like that in slide 1, I have Spam (but without any content), and in slide 3, I have Spam and Eggs. How can I achieve this?

An alternative would be to use a tabular environment, but I'm interested to see if it can be achieved with a description.

Answer 1

Something like this works:

\documentclass{beamer}

\newcommand\desctext[1]{%
  \only<+(1)>{\mbox{}}%
  \onslide<+(1)->{#1}}

\begin{document}

\begin{frame}
\begin{overprint}
\begin{description}
\addtocounter{beamerpauses}{-1}
\item[Spam1]\desctext{Eggs1}
\item[Spam2]\desctext{Eggs2}
\item[Spam3]\desctext{Eggs3}
\item[Spam4]\desctext{Eggs4}
\addtocounter{beamerpauses}{1}
\end{description}
\end{overprint}

\end{frame}

\end{document}

For the ordering required (all labels first, then all descriptions), something like this can be done:

\documentclass{beamer}

\newcommand\desctext[2][]{%
  \only<+(1)->{\mbox{}}%
  \onslide<#1->{#2}}

\begin{document}

\begin{frame}
\begin{overprint}
\begin{description}
\addtocounter{beamerpauses}{-1}
\item[Spam1]\desctext[5]{Eggs1}% add one to the number of items
\item[Spam2]\desctext[6]{Eggs2}
\item[Spam3]\desctext[7]{Eggs3}
\item[Spam4]\desctext[8]{Eggs4}
\addtocounter{beamerpauses}{1}
\end{description}
\end{overprint}
\end{frame}

\end{document}

Answer 2

Personally I use itemize environment to achieve your goal.

description environment seems to behave differently from itemize and enumerate environment for "complicated" constructions.

\documentclass{beamer}
\begin{document}
\begin{frame}
\begin{overprint}
\begin{itemize}
\item<1-> Spam:
\onslide<2->{Eggs}
\end{itemize}
\end{overprint}
\end{frame}
\end{document}