[Tex/LaTex] How to set default line spacing in a .cls file

documentclass-writingline-spacingsetspace

I am writing a document class where I want to set the default line spacing to be 1.5. How can I use the setspace package to achieve this? More particularly, where in my .cls file should I mention \onehalfspacing?
I have tried modifying \baselinestretch, but it does not work when I add \RequirePackage{setspace} in the .cls file.

Best Answer

The error in your comment says, that \@currsize is undefined. It is set by \@setfontsize, which is called by LaTeX font size commands such as \Large, \small etc.

So you could fix it by defining \@currsize yourself, such as by

\let\@currsize\normalsize

but I recommend to define a font size in your class before you load setspace, which fixes it. Here's an example from bk10.clo, loaded by the book class:

\renewcommand\normalsize{%
   \@setfontsize\normalsize\@xpt\@xiipt
   \abovedisplayskip 10\p@ \@plus2\p@ \@minus5\p@
   \abovedisplayshortskip \z@ \@plus3\p@
   \belowdisplayshortskip 6\p@ \@plus3\p@ \@minus3\p@
   \belowdisplayskip \abovedisplayskip
   \let\@listi\@listI}
\normalsize
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