From: "Berger, Daniel" <Daniel.Berger@...>
Date: 2005-10-21T23:32:20+09:00
Subject: Re: A comparison by example of keyword argument styles

> -----Original Message-----
> From: Trans [mailto:transfire@gmail.com] 
> Sent: Friday, October 21, 2005 8:12 AM
> To: ruby-talk ML
> Subject: Re: A comparison by example of keyword argument styles

<snip>

> Perhaps we should just sing a song and "Let's Call The Whole 
> Thing Off".

Heh.  Thought about it.

> If keywords integrate the interface too tightly 
> with the code, then why tie them to the interface? Also, I 
> imagine there many be many more keyword arguments then 
> ordered args, this will make for some very LONG constructors:
> 
>   def stadium( height:, seating_capacity:, location:, color:, 
> sports:, concessions:, extra_features:, indoor:, yadayadayada: )
> 
> So maybe just treat named parameters like blocks. You can 
> have em or not. But you don't need to define them in the 
> interface. Currently I do a lot of
> 
>   def( *args )
>     keys = args.last.is_a?(Hash) ? args.pop : {}
>     a,b,c = *args
> 
> If I could just do
> 
>   def( a, b, c, **keys )
>     ...
> 
> I'd be happy enough.

I'm glad you brought this example up.  What do you do when you have a
ton of accessors in your class?  I have just such a case with the Format
class in the spreadsheet package, where you have "font_name",
"font_size", "border_color", etc.  About 30 accessors I think.

The solution here is NOT keywords arguments (regardless of
implementation), where you would end up with ridiculously long
constructors, as you mentioned.  It's the old "yield self if
block_given?" trick:

class Format
   attr_accessor :font_color, :font_size, :bold # ...
   def initialize
      yield self if block_given?
   end
end

format = Format.new do |f|
   f.font_color = "blue"
   f.font_size  = 10
   f.bold       = true
   ...
end

Regards,

Dan