From: Austin Ziegler <halostatue@...>
Date: 2004-08-06T02:50:41+09:00
Subject: Re: Macros in Ruby

On Fri, 6 Aug 2004 01:31:28 +0900, Ara.T.Howard <ahoward@noaa.gov> wrote:
> i actually use them quite a bit and would appreciate a shortcut. i sometimes
> prefer to have modifiable Proc attributes of object to parameterize their
> behaviour rather than messing with inheritence or dynamic redefinition. i
> also end up writing methods which take options callbacks for
> debugging/logging, eg:

I'd do this as:

  def long_db_update(arg, callback = nil)
    sql = gen_sql(arg)

    callback.pre(sql) if callback.respond_to?(:pre)

    res =
      if callback.respond_to?(:pan)
	t = Thread.new(Thread.current) do |c|
	  begin
	    execute(sql)
	  rescue => e
	    c.raise (e)
	  end
	end

	loop do
	  break unless t.status
	  callback.pan(get_state)
	  sleep 0.42
	end

	t.join
	t.value
      else
	execute(sql)
      end

    callback.post(res) if callback.respond_to?(:post)
    res
  end

Then I can create my callback object. With this, I could easily plug
in a debug object (predefined), a GUI object, or anything else, and
my callback becomes part of my defined API. (I would actually even
go as far as modifying callback.post so that its return may
optionally modify res.)

-austin
-- 
Austin Ziegler * halostatue@gmail.com
               * Alternate: austin@halostatue.ca