Aczid's blog

If you're a programmer, chances are you're not a big fan of making software diagrams. Writing code is much more fun!
Of course, if you remain agile you can do a whole project by yourself. But say you are using rails in a professional environment? Sooner or later, you're going to want to show someone a global overview of how your app is structured.
In my opinion, diagrams are good to reach agreement on the design of software.

It should be easy to maintain,
it shouldn't all be written in advance, and
it definetly shouldn't be a product in and of itself.

Since we're lazy ruby programmers, why not turn the waterfall upside down and generate diagrams from our code?
Go and get Railroad. Its needs Graphviz to work. You can get railroad as a gem and graphviz is hopefully in your package manager.
After getting those, just try it out on your current project!

Generate a model diagram from your app including non-ActiveRecord models and inheritance.

 $ railroad -M -a -i | dot -Tpng > doc/models.png

Generate a controller diagram.

 $ railroad -C | neato -Tpng > doc/controllers.png

Check out the railroad site for more info, code examples and some sample output. The output actually looks pretty neat. Here's what it generates for Typo.