How to define default options to a class?

Question

I do not undestand how to pass options to the parent class when writting a child class. I tried several possibilities but I never get flush left aligned equations.

I do understand the difference between LoadClass and LoadClassWithOptions but I think this is not the problem here. The uncommented lines correspond to what I understand from the document clsguide.pdf but it does not work.

\RequirePackage{filecontents}

% my class file
\begin{filecontents}{baz.cls}
\PassOptionsToClass{fleqn}{article}
\ProcessOptions\relax
%\LoadClass[fleqn]{article}
\LoadClass{article}
%\LoadClassWithOptions{article}
\RequirePackage{amsmath}
\end{filecontents}

\documentclass{baz} 
%\documentclass[fleqn]{baz} 

\usepackage{lipsum}

\begin{document}
\lipsum[1]
\begin{equation*}
    e^{i\pi} + 1 = 0
\end{equation*}
\lipsum[2]
\end{document}

Answer 1

The confusion in this example is coming from the fact that it is really the amsmath package that needs to know about the fleqn option. As it stands you are passing no options to amsmath. One working set up would be:

baz.sty:

\DeclareOption*{\PassOptionsToClass{\CurrentOption}{article}}
\ProcessOptions\relax
\LoadClass[fleqn]{article}
\RequirePackage[fleqn]{amsmath}

tex file:

\documentclass[a4paper]{baz} 

\usepackage{lipsum}

\begin{document}
\lipsum*[1]
\begin{equation*}
    e^{i\pi} + 1 = 0
\end{equation*}
\lipsum[2]
\end{document}

Here you see additional options being passed on to the class, which is loaded additionally with fleqn option. The package amsmath is loaded with the fleqn option too. In this case, it may well be the package option is unnecessary, but this mimics the effect of

\documentclass[fleqn]{article}
\usepackage{amsmath}