From: "Ara.T.Howard" <ahoward@...>
Date: 2004-07-26T22:41:54+09:00
Subject: Re: code introspection

On Mon, 26 Jul 2004, Daniel Cremer wrote:

> Hi,
>
> Is there a solution to do code introspection rather than introspection
> at the level of the Module/Object ? I can't figure out if I'm looking
> for something that isn't there in Ruby since I've been reading C# code
> or if I'm missing something. Let me explain my problem.
> I would like to load ruby source files and dynamically create objects
> from classes located inside these sources. It's one class/object per
> source file and I can  make it so that a string from a configuration
> file holds the name of the class. However I can't figure out a good
> way to use that string to get to the class in the source file.
>
> I could use eval but am really uncomfortable with that for obvious
> reasons (people keep saying it's evil so I don't play with him). The
> other solution I came up with was to add a method in the same source
> but outside the class to return the desired object:
>
> --------------source file---------
> class MyNewClass
> ...
> end
>
> def create_loaded_class()
>  return MyNewClass.new()
> end
> ---------------------------------
>
> Then as I require the source files I can successively invoke the
> create_loaded_class method. This works but can get quite messy as
> there are a lot of things to consider if you need to reload sources
> and create new objects etc.
> Please tell me I'm missing something obvious :).
>
> thanks,
> Daniel


   ~ > cat c.rb
   files = %w(a.rb b.rb)

   files.each do |file|
     load file
     name, klass = Common.introspect file
     p name
     p klass
     klass.new
   end


   ~ > ruby c.rb
   "Foo"
   Common::Foo
   "foo"
   "Bar"
   Common::Bar
   "bar"


   ~ > cat a.rb
   module Common
     class Foo
       def initialize
         p 'foo'
       end
     end

     class << self
       def introspect path
         @introspect[File.basename(path)]
       end
     end
     @introspect = {} unless defined? @introspect
     @introspect[File.basename(__FILE__)] = 'Foo', Foo
   end


   ~ > cat b.rb
   module Common
     class Bar
       def initialize
         p 'bar'
       end
     end

     class << self
       def introspect path
         @introspect[File.basename(path)]
       end
     end
     @introspect = {} unless defined? @introspect
     @introspect[File.basename(__FILE__)] = 'Bar', Bar
   end


you could obviously do this without the 'Common' module - but i think it's
cleaner/safer this way - provided you can manage to wrap all your modules this
way...

kind regards.

-a
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