From: Robert Klemme <bob.news@...>
Date: 2004-02-27T17:44:52+09:00
Subject: Re: Callback


"Han Holl" <han.holl@pobox.com> schrieb im Newsbeitrag
news:b93fa83f.0402260928.25ffbd4a@posting.google.com...
> Hi,
>
> The following code works, but I was wondering if the creation of the
@obj
> instance variable is really necessary?

It is not.  I'd consider it harmful since you will have problems defining
more than one callback this way.  Solutions that others have proposed are
far betters since they store 'obj' in a closure.  So you can invoke
#callback arbitrarily often.

I wonder though what you are trying to achieve.  It looks quite
complicated to me and currently I don't have a clue about the real world
problem you are trying to solve.

Regards

    robert


> class A
>   def callback(name, obj)
>     @obj = obj
>     eval("def #{name}; @obj.keys; end")
>   end
> end
>
> class B
>   attr_reader :keys
>   def initialize(k, cb)
>     @keys = k
>     cb.callback('cassette', self)
>   end
> end
>
> a = A.new
> g = B.new([1,2,3], a)
> puts a.cassette