I was just trying to create coding that reflectively loads the subclasses of a class I’ve defined. The idea is that as new subclasses are added, the script I’m writing can detect which ones are present and inform a remote API that support for a specific API feature is available.

I had executed the method once on the class, and it did return the name of the subclass that I had defined and checked for the existence of in the Rails console environment. Then I added other subclasses, reloaded (reload!), and ran the method once again. This time I got nothing but an empty array returned. It turns out that Rails 3 uses autoloading for classes…so the subclasses have to be referenced at some point, and thus loaded into memory, before the subclasses method will include them in the list.