From: "David A. Black" <dblack@...>
Date: 2005-09-18T21:28:56+09:00
Subject: Re: Finding out if a method is already redefined

Hi --

On Sun, 18 Sep 2005, Michael Schuerig wrote:

>
> My problem occurs in the context of Rails, but is really core Ruby. In
> its "development environment" Rails uses load, not require, to load
> files anew for each request. This is to enable changes to the running
> application. I'm running into a problem with this mechanism when
> redefining a method *and* referring to the old method in the redefined
> one. When this redefinition happens twice, it results in an infinite
> recursion. I've tried to guard the redefinition with a check for the
> new method, but this doesn't work, the new alias is not recognized.
>
>  unless method_defined?(:method_new)
>    alias_method :method_old, :method
>    def method_new(options = {})
>      ...
>      method_old(options)
>    end
>    alias_method :method, :method_new
>  end
>
> What do I have to do to make this work?

I can't duplicate your problem.  Here's what I'm doing:

# l.rb:
class C
   def meth
     puts "old"
   end
end
c = C.new
c.meth
load 'load.rb'
c.meth
load 'load.rb'
c.meth

# load.rb
class C
   unless method_defined?(:meth_new)
     alias_method :meth_old, :meth
     def meth_new
       puts "new"
       meth_old
     end
     alias_method :meth, :meth_new
   end
end

# output of running l.rb:
old
new
old
new
old


David

-- 
David A. Black
dblack@wobblini.net