From: dblack@...
Date: 2006-07-27T09:47:27+09:00
Subject: Re: Issue extending a delegated class

Hi --

On Thu, 27 Jul 2006, rak rok wrote:

> Hi,
>
> I have a simple class that I'm extending via delegation:
>
> class A
> def one ; puts "A::one" ; two ; end
> def two ; puts "A::two" ;       end
> end
>
> class B < SimpleDelegator
>
> def initialize
>   a = A.new
>
>   # do some stuff to a
>
>   __setobj__ a
>   super( a )
> end
> end
>
>
> I then instantiate B, and use that, all is well.  However, i'm running into
> issues whenever I try to override a method in B:
> b = B.new
> class << b

You're not overriding anything in B here; rather, you're adding an
instance method to the singleton class of the instance b.

> def two ; puts "foo" ; end
> end
>
> I would have expected b.one to output:
> A::one
> custom

(Do you mean "foo" rather than "custom"?)

> But instead i get:
> A::one
> A::two
>
> However, calling the overriden method directly produces the expected
> result.  I'm guessing the extend is really only adding the function to the B
> instance and not to A?  Is there a way to get to A?

Your guess is right :-)  When a handles the delegate call to #one,
part of that call is a call to #two -- which, as far as a is
concerned, is A#two.

You can always override A#two, but I imagine that's not what you have
in mind.  I'm not sure exactly what you are trying to do, though.


David

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