From: Xavier Noria <fxn@...>
Date: 2010-02-11T18:12:52+09:00
Subject: Re: Newbee question. Runtime classloading

Ruby needs to interpret the file where the class is defined before you
can use it. Interpreting the file has the side-effect of defining the
constant, which is in turn a side-effect of the class keyword.

As you surely know that is typically done with require, and if the
parsers are unknown beforehand you can just use Dir[] with a glob to
require whatever has some filename pattern in a loop or something. I
mean, require is a method you can call it wherever you want.

Rails does not need that because it offers class/module autoloading:
if the filename is named after the class using some common sense
conventions, and lives in some of the standard directories,
app/something, lib, etc., then the dependencies mechanism goes and
loads it for you the first time the constant is used. That is
accomplished basically via a Ruby hook called const_missing that is
triggered when that initial failure happens.