From: Trans <transfire@...>
Date: 2005-10-23T10:22:01+09:00
Subject: Re: A comparison by example of keyword argument styles


Bill Guindon wrote:

> It's always seemed strange to me that the two formats differ, seems a
> nuisance when you've built up either the attr_accessor list, or your
> parameter list, and you have to hand massage one to the other.
>
> class Format
>   attr_accessor :font_face, :font_color, :font_size, :bold, :italic
>   def initialize
>     parameters :font_face='arial'
>     keywords :font_color='black', :font_size, :bold=false, :italic=false
>     ...
>   end
> end
>
> format = Format.new('verdana')
> format = Format.new(font_size: 1, bold: true)
> format = Format.new('verdana', italic: true, font_size: 10)
>
> granted, functon calls and constructors could still get quite lengthy.

But you can mitigate that. Also there's no need for this on regular
parameters, they can remain pretty much the same, though something like
this might be nice default values. Anyway:

 class Format
   attr_accessor :font_face, :font_color, :font_size, :bold, :italic
   def initialize(font_face='arial')
     key :font_color=>'black'
     key :font_size
     key :bold=>false
     key :italic=>false
     ...
   end
 end

or just

 class Format
   attr_accessor :font_face, :font_color, :font_size, :bold, :italic
   def initialize(font_face='arial')
     keys :font_size,
          :font_color=>'black',
          :bold=>false,
          :italic=>false
     ...
   end
 end

Though I am not using the new named parameters for the #keys method
itself here. Even so this is kind of nice. It's kind of like the lisp
stuff too. And in a way it's like a "keywords block", in fact:

 class Format

   attr_accessor :font_face, :font_color, :font_size, :bold, :italic

   def initialize(font_face='arial') keys :font_size,
                                          :font_color=>'black',
                                          :bold=>false,
                                          :italic=>false
     puts "keeps the keys out ot the paranthetical"
   end

 end

The only things is that means key/keys becomes a keyword (no pun
intended). At least I think it would. Well, in that case we could take
it a bit further and pull a page out of Alex' book -- it might be even
nicer to predefine these keys:

 class Format

   attr_accessor :font_face, :font_color, :font_size, :bold, :italic

   initkeys = keys :font_size,
                   :font_color=>'black',
                   :bold=>false,
                   :italic=>false

   def initialize( font_face='arial', *initkeys )
     puts "keeps the keys out ot the paranthetical"
   end

 end

Then they be reusable. Could extend this to parameters in general too.

T.