12.14.13 \PassOptionsToClass & \PassOptionsToPackage

Synopses:

\PassOptionsToClass{options}{clsname}
\PassOptionsToPackage{option}{pkgname}

Adds the options in the comma-separated list options to the options used by any future \RequirePackage or \usepackage command for the class clsname or the package pkgname, respectively.

The reason for these commands is that although you may load a package any number of times with no options, if you can specify options only the first time you load the package. Loading a package with options more than once will get you an error like Option clash for package foo.. LaTeX throws an error even if there is no conflict between the options.

If your own code is bringing in a package twice then you can combine the calls; for example, replacing the two

\RequirePackage[landscape]{geometry}
\RequirePackage[margins=1in]{geometry}

with the single command

\RequirePackage[landscape,margins=1in]{geometry}

However, suppose you are loading firstpkg and inside that package it loads secondpkg, and you need secondpkg to be loaded with option draft. Then before load the first package you must tell LaTeX about the desired options for the second package, like this:

\PassOptionsToPackage{draft}{secondpkg}
\RequirePackage{firstpkg}

If firstpkg.sty loads an option in conflict with what you want then you may have to alter its source, or yours.

These commands are useful for general users as well as class and package writers. For instance, suppose a user wants to load the graphicx package with the option draft and also wants to use a class foo that loads the graphicx package, but without that option. The user could start their LaTeX file with \PassOptionsToPackage{draft}{graphicx} \documentclass{foo}.