From: Sergey Sheypak <serega.sheypak@...>
Date: 2010-02-11T18:32:45+09:00
Subject: Re: Newbee question. Runtime classloading

Xavier Noria wrote:
> Ruby needs to interpret the file where the class is defined before you
> can use it. 
I understand it.

>Interpreting the file has the side-effect of defining the
> constant, which is in turn a side-effect of the class keyword.
don't get idea with side-effects


> 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.
Something like:
require "parsers/parser_format#{@format_version.gsub(/\./, '_')}"
clz = "ParserFormat#{@format_version.gsub(/\./, '_')}"
parser_impl = Kernel.const_get(clz)
works nicely!

> 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.
Thanks!
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