From: "T. Onoma" <transami@...>
Date: 2003-11-22T20:36:18+09:00
Subject: Re: Method wrapper question (was "stereotyping (was ...))

On Saturday 22 November 2003 07:19 am, Gavin Sinclair wrote:
> I'm not buying into the interface debate one way or the other, but a
> related question here is: how do you envisage :pre, :post, etc.,
> working if they are defined multiple times?

I have considered this too. I would like to propose an alternate/augmenting 
syntax that has a simple definite rule for how they work together:

  def dothis
    print "A"
  end

  def dothis
  pre
    print "B"
  post
    print "C"
  end

dothis  # => BAC

  def dothis
  pre
    print "E"
  post
    print "D"
  end

  dothis # =>  EBACD

  def dothis
  pre
    print "F"
  main
    print "Z"
  post
    print "G"
  end

  dothis # =>  FEZDG

This final result might seem odd at first, but it is a very simple system. 
Every subsequent definition of a pre and/or post, causes the latter to become 
part of main. Thus every method has a pre, main and post once defined and 
every subsequent addition moves them a step inward to main. 

Another example, this time with : syntax.

  def dothis
    print "A"
  end

  def dothis:post
    print "B"
  end

  dothis  # => AB

  def dothis:post
    print "C"
  end

  dothis  # => ABC

  def dothis:main
    print "Q"
  end

  dothis  # => QC

  def dothis
    print "Z"
  end

  dothis  # => Z  (still can redefine)


What do you think?

-t0