From: Robert Klemme <bob.news@...>
Date: 2006-03-23T22:48:52+09:00
Subject: Re: Is this a kind of design patterns?

Jim Weirich wrote:
> Robert Klemme wrote:
>> IMHO this is not thread safe.  If you need the method interface, you
>> could do something like
> [...]
>> :-)
> 
> I did catch the smiley.  :)

:-)

> Given that the original returned a new object on every invocation, a 
> race condition that might generate an extra light weight object or two 
> at initialization seems to be a low risk.
> 
> However, if I were really concerned about the race condition, I think I 
> would go the metaprogramming route rather then the dynamic lookup route. 
> Something more like this:
> 
>   class Color
>     ...
>     class << self
>       private
>       def define(name, color)
>         class_eval "#{name.to_s.upcase} = color"
>         class_eval "def Color.#{name}; #{name.to_s.upcase}; end"
>       end
>     end
> 
>     define :red, Color.new(255, 0, 0)
>     ...
>   end
> 
> ;)

:-)

Since we're in Color anyway, you can simplify the definition that by

   class Color
     # ...
     class << self
       private
       def define(name, *args)
         cname = name.to_s.upcase
         col = const_set( cname, new(*args))
         class_eval "def self.#{name}; #{cname}; end"
       end
     end

     define :red, 255, 0, 0
     # ...
   end

:-)

Kind regards

	robert