From: Mauricio Fernandez <mfp@...>
Date: 2006-06-01T22:56:53+09:00
Subject: Re: An alternative to the class Foo < Struct.new(vars) idiom and SuperStruct

On Thu, Jun 01, 2006 at 09:33:29PM +0900, Jeff Rose wrote:
> I'm sold.  This will be great for easily defining event types in 
> EventMachine.  Why the complicated default argument values though?  For 
> simple cases how about just using hash syntax:
> 
> MyClass = SuperClass.new(:a => 2, :b => 3)

The problem with this is that it makes positional arguments impossible, since
the Hash doesn't preserve the order; maybe 

    MyClass = SuperClass.new(:a, 2, :b, 3) 
or 
    MyClass = SuperClass.new(:a, :b, :a => 2, :b => 3)  
    # (don't like the repetition though)
?

Anyway, I realized I can remove a couple lines from SuperClass to turn the
following (which I forgot to show in the previous msg) into the preferred
style:
  # b is optional only when using the keyword arg style
  class Foo < SuperClass.new(:a, :b)
    def initialize(*args)
      super
      @b ||= "foo"   
    end
  end

which will look better than passing a block to SuperClass.new for most people.


Maybe I should allow both styles:
* mandatory keyword arguments, with default values specified in the
  SuperClass.new call (have to define how, two possibilities given above but
  there's probably a better way)
* either full positional arguments or keyword arguments (at least one required
  to discriminate), default values set manually in #initialize as in the above
  example.

The desired one could be specified either via an explicit call
(SuperClass.new_kw_args vs. SuperClass.new_positional ?) or implicitly by the
arguments given to SuperClass.new. 

It's all easy to implement but there are many options...

-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby