From: Joel VanderWerf <vjoel@...>
Date: 2008-05-14T01:53:34+09:00
Subject: Re: requiring the same file and capturing the constants

Raj Singh wrote:
> file1.txt
> -----------------
> class Person
> end
> module Speak
> end
> 
> 
> The task is to printout all the constants listed in the file. In this
> case there are Person and Speak.
> 
> I need to handle two cases.
> 1) The system loads the file for the first time. I guess in this case I
> can use ObjectSpace.each_object or ObjectSpace.some_method from API to
> get before and after picture. Subtract the before picture and I will get
> the constants.
> 
> 2) The second case is when file1.txt is already loaded into the
> application. So in this case I can't do before and after thing. How can
> I get constants in this case without before and after picture.
> 
> Thanks

If you have control over *how* the file is loaded, you can do this, 
using http://redshift.sourceforge.net/script:

[~/tmp] cat file.rb
class Person
end
module Speak
end
[~/tmp] cat main.rb
require 'script'
mod = Script.load 'file.rb'
p mod.constants
[~/tmp] ruby main.rb
["Person", "Speak"]

The trick is really just reading the file, creating a module, and 
calling module_eval on that with the contents of the file.

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407