The TutsPlus.com site has posted the next tutorial in their "Object-Oriented Autoloading in WordPress" series - part two - expanding on the basics presented in the previous part of the series.

In the previous tutorial, we covered a handful of concepts, all of which are going to be necessary to fully understand what we're doing in this tutorial. Specifically, we covered the following topics: object-oriented interfaces, the single responsibility principle, how these look in PHP [and] where we're headed with our plugin.

[...] Ultimately, we won't be writing much code in this tutorial, but we'll be writing some. It is, however, a practical tutorial in that we're performing object-oriented analysis and design. This is a necessary phase for many large-scale projects (and something that should happen for small-scale projects).

First they briefly cover the environment you'll need to follow along (already set up if you followed along with part one). They then get back into the code, evaluating the current state of the custom autoloader and investigating how it can be broken down into a class and a set of methods instead of procedural code. They work through the different functional parts of the autoloader and how to break it down into classes with only one job (the "single responsibility principle"). They end up with the autoloader that uses NamespaceValidator, FileInvestigator and FileRegistry instances to get the job done.