From: dblack@...
Date: 2003-01-14T07:59:44+09:00
Subject: Re: Array_Of(AClass)

Hi --

On Mon, 13 Jan 2003, Gavin Sinclair wrote:

> I want to highlight this: from a singleton class, you can use "super"
> like in normal inheritance.  Keep this in mind if you are redefining
> methods anytime.  I find the pattern
>
>   alias_method :old_xxx, :xxx
>
>   def xxx
>     ...
>     old_xxx
>     ...
>   end
>
> rather smelly.  Much better is
>
>   class << obj
>     def xxx
>       ...
>       super
>       ...
>     end
>   end
>
> I just learned that through this exercise, so I'm glad some good came
> of it.

Technique #2 is not a drop-in replacement for technique #1, though.
For example, if you want to "listen in" on what a method is doing,
you might do:

  class String
    alias :oldsplit :split
    def split(*a)
      puts "args are #{a.join(', ')}"
      oldsplit(*a)
    end
  end

I don't think there's an equivalent way to do this by modifying the
object's singleton class.


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav