From: Robert Klemme <bob.news@...>
Date: 2005-06-07T23:40:26+09:00
Subject: Re: making a duck

Eric Mahurin wrote:
> --- nobu.nokada@softhome.net wrote:
>> At Tue, 7 Jun 2005 11:59:47 +0900,
>> Eric Mahurin wrote in [ruby-talk:144750]:
>>> Is there an advantage to having a separate Behavior class
>> as
>>> opposed the solution I had: making a singleton Object
>> directly?
>>
>> To allow sharing same behavior.
>
> I'm not sure how much application this would have over the
> conventional class definition approach.
>
> At first I didn't think this would work because I thought you
> wouldn't be able to create any instance variables using
> define_method.  I thought any @ variables in a proc would refer
> to the @ variable in the original context, but define_method
> apparently rebinds them to the object.

I always remind myself that the binding of "self" changes - even for each
method invocation.  This explains pretty good why this works as it should.

16:31:18 [ruby]: ruby x.rb
4
666
666
16:38:10 [ruby]: cat x.rb
o=Object.new
def o.size() 666 end
x="test"

class<<o;self;end.class_eval do
  define_method(:test) do
    puts x.size
    puts self.size
    puts size
  end
end

o.test
16:38:14 [ruby]:

Kind regards

    robert