Hide/unhide questions using a command like \printquestions in exam.cls

Question

I am trying to customize the question environment of exam.cls. I want to have a command like \printquestions to hide/unhide the questions, while retaining the points and question labels.

I have used environ package to create an enviroment around each question content to do this.

\newif\ifkeepquestion \keepquestiontrue
\NewEnviron{qsn}{\ifkeepquestion\BODY\fi}

\begin{document}

\begin{questions}
\pointsdroppedatright

%1
\question[10]
\begin{qsn}
Describe the effect on the balloon industry.
\end{qsn}
\droppoints

\end{questions}

\end{document}

Is there is any direct way to hide the content "Describe the effect on the balloon industry." inside the exam.cls, rather than relying on Environ package.

I tried to look into the \newenvironment{questions} of exam.cls file, where it uses \list command and \item to create the content. Can we modify the \item definition to either hide or unhide the content, based on \ifkeepquestion

Answer 1

This will show the question number (and the points) but not the question itself. The question itself will not break over pages and will exhibit hanging indentation (I forget whether that is normal).

Apparently, \question sets local values which will not be preserved if placed inside an environment. You would need to dig into the code, find them and set them globally.

\documentclass{exam}

\newif\ifkeepquestion \keepquestionfalse
\newsavebox{\questionbox}

\newenvironment{qsn}{\begin{lrbox}{\questionbox}\minipage[t]{\linewidth}}%
{\endminipage\end{lrbox}\ifkeepquestion \usebox\questionbox  \fi}

\begin{document}
\begin{questions}
\pointsdroppedatright

\question[10]\begin{qsn}
Describe the effect on the balloon industry.
\end{qsn}
\droppoints

\end{questions}
\end{document}

---

This modifies \question inside the savebox just to steal the points argument. It includes a number of patches (outside the savebox) needed to get \droppoints to work.

\documentclass{exam}
\usepackage{showframe}
\usepackage{etoolbox}

\newif\ifkeepquestion \keepquestiontrue
\newsavebox{\questionbox}
\newcommand{\pointsarg}{}% reserve global name

\makeatletter
\newenvironment{qsn}{\begin{lrbox}{\questionbox}%
  \minipage[t]{\linewidth}%
    \renewcommand{\question}[1][0]{\xdef\pointsarg{##1}}}% local definition
{\endminipage\end{lrbox}%
  \question[\pointsarg]%
  \ifkeepquestion
    \usebox\questionbox
  \fi}

\patchcmd{\@readpoints}{\def\@points}{\gdef\@points}{}{FAILED}
\patchcmd{\item@points@pageinfo}{\def\padded@point@block}{\gdef\padded@point@block}{}{1}
\patchcmd{\item@points@pageinfo}{\def\padded@point@block}{\gdef\padded@point@block}{}{2}
\makeatother

\begin{document}
\begin{questions}
\pointsdroppedatright

\begin{qsn}\question[10] Describe the effect on the balloon industry.  
Yada yada yada yada yada yada yada yada yada yada yada yada yada yada yada yada yada yada yada.
\end{qsn}

\droppoints

\end{questions}
\end{document}