From: Jakub Travnik <j.travnik@...>
Date: 2001-11-25T00:38:11+09:00
Subject: [ruby-talk:26340] Re: dynamically redefining methods

try this:

module Loggable
   def self.append_features(klass)
     klass.instance_methods.each do |method|
       klass.class_eval "  alias ___#{method} #{method};"+
	"  def #{method}(*params,&block);"+
	"    ___#{method}(*params,&block);"+
	"    puts 'call to #{method} logged';"+
	"  end;"
     end
   end
end

class Test
   def foo
     puts "hello world"
   end
   def bar
     puts "hello universe"
   end
   include Loggable
end

Jakub Travnik
jabber://jtra@jabber.com
ICQ: 66770334 (deprecated)


Massimiliano Mirra wrote:

> I would like to include logging capabilities to a class by just
> including a module.  This is what I have tried:
> 
> 
> module Loggable
>   def self.append_features(klass)
>     klass.instance_methods.each do |method|
>       eval "class #{klass}"
>       eval "  def #{method}"
>       eval "    super"
>       eval "    puts 'call to #{method} logged'"
>       eval "  end"
>       eval "end"
>     end    
>   end
> end
> 
> class Test
>   def foo
>     puts "hello world"
>   end
>   def bar
>     puts "hello universe"
>   end
>   include Loggable
> end
> 
> Apparently, the eval'ed code in Loggable does not work because of its
> context, i.e. a class definition does not begin to a method inside a
> module.  Can this be worked around?  Or are there better ways to
> accomplish this?
> 
> Massimiliano
> 
>