From: zdennis <zdennis@...>
Date: 2006-04-11T22:56:14+09:00
Subject: Re: Identfying classes in a file dynamically

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Navya Amerineni wrote:
> Hi,
> 
> I was trying to identify the classes in a give file at the run time. the following is the code i used.
> sc, ec = [], []
> ObjectSpace.each_object(Class) { |c| sc << c }
> require 'Roman.rb'
> ObjectSpace.each_object(Class) { |c| ec << c }
> new_classes = ec - sc
> puts new_classes
> sc, ec = [], []
>  ObjectSpace.each_object(Class) { |c| sc << c }
>  require 'Roman1.rb'
>  ObjectSpace.each_object(Class) { |c| ec << c }
>  new_classes = ec - sc
> puts new_classes
>  
> Both roman.rb and roman1.rb has the same class Roman.
> the first time i print the new_classes i can see the Roman class in the output but the second one does not print because the class Roman is arleady read previously.
> 
> is there a way i can over come this problem and identify the Roman class twice.
> 
> 

Way #1, store the new classes in a hash. This way you won't be overriding any classes you've previously loaded.

Way #2, use one array to store new classes, and then each time you compute the "new_classes" after you load a file, merge those
into your one authoriatize array. This way you won't be overriding any classes you've previously loaded.

Way #3, pass a string into a new ruby process which loads the files and outputs the new classes. Read these in and then use Way #1
or Way #2 to store the classes. This is a bit hackish, but it works and it leaves your toplevel ruby process namespace alone.

Here is the idea of Way #3

  str =<<-'EOT'
    def count_classes( arg )
      arr = []
      ObjectSpace.each_object( arg ){ |c| arr << c }
      arr
    end

    orig_classes = count_classes( Class )
    require "load"
    new_classes = count_classes( Class ) - orig_classes
    puts new_classes.join( "\n" )
  EOT

  child = IO.popen( "ruby -e '#{str}'", "r" )
  new_classes = child.readlines.map!{ |s| s.chomp! }
  puts new_classes

Zach
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