From: ara.t.howard@...
Date: 2006-05-04T12:00:35+09:00
Subject: Re: Ruby idiom for attributes / properties

On Thu, 4 May 2006, John Lam wrote:

> I'm writing a bunch of auto-marshaling code to let CLR code call back into
> Ruby. I just got the simplest possible marshaling scenario working today,
> which is letting you bind an Array of ActiveRecord objects to a CLR
> DataGridView control. See
> http://www.iunknown.com/articles/2006/05/03/activerecord-and-windows-formsfor
> a longer discussion and a screenshot.
>
> Bottom line is that I can now write:
>
> data_grid.data_source = Person.find_by_last_name('Lam')
>
> Now, here's my problem: I'm not all that happy that I'm special casing my
> code for ActiveRecord objects. However, since Ruby doesn't have a mechanism
> for runtime-discovery of attributes, I'm special casing for ActiveRecord
> since it provides an @attributes hashtable with the name-value pairs for all
> attributes in the object. This makes it easy for me to generate the CLR
> anonymous class + object that implements the marshaling code that retrieves
> the attribute data from the Ruby ActiveRecord object (think about this as
> marshal by reference).
>
> Do folks have suggestions for implementing a discoverable attribute /
> property idiom in Ruby? Perhaps via a mixin module in the standard library?
> Or has this been done already and I'm just showing my Ruby newbiness?
>
> Thanks
> -John
> http://www.iunknown.com

   harp:~ > cat a.rb
   require 'traits'

   class C
     trait 'a'
     traits 'b' => 42, 'c' => 42.0
     class_trait 'a'
   end

   p C.class_traits
   p C.traits


   harp:~ > ruby a.rb
   [["a", "a="]]
   [["a", "a="], ["b", "b="], ["c", "c="]]


and a whole lot more

   http://rubyforge.org/projects/codeforpeople/
   http://codeforpeople.com/lib/ruby/traits/traits-0.8.0/README

regards.

-a
-- 
be kind whenever possible... it is always possible.
- h.h. the 14th dali lama