From: Rich Kilmer <rich@...>
Date: 2001-10-07T03:58:32+09:00
Subject: [ruby-talk:22165] RE:  Creating external accessors for class constants

Yes...I am replying to myself...

you can access a constant by:

- class::constant

or "Airlines::AA"

I did not realize this :)

> -----Original Message-----
> From: Rich Kilmer [mailto:rich@infoether.com]
> Sent: Saturday, October 06, 2001 2:41 PM
> To: ruby-talk ML
> Subject: [ruby-talk:22164] Creating external accessors for class
> constants
> 
> 
> I find myself wanting to use class constants more globally in my 
> code.  Because of Ruby's encapsulation rules, every attribute 
> (and constant) is private.  A helper method exists on Module to 
> simplify externalizing attributes:
> 
> attr, attr_accessor, attr_reader, attr_writer
> 
> I was wondering whether it would make sense to have a similar 
> method for class constants?
> 
> const_reader
> 
> defined as follows....
> 
> # add the const_reader method to Module
> class Module
>   def const_reader(*symbols)
>     symbols.each do |symbol| 
>       class_eval "def #{self.name}.#{symbol.to_s}; #{symbol.to_s}; end"
>     end
>   end
> end
> 
> # define constants and export them via const_reader:
> class Airlines
>   AA="American Airlines"
>   BA="British Airways"
>   const_reader :AA, :BA
> end
> 
> # These constants are now accessible via class methods (publicly)
> # but (still) as constants internal to the class (no method overhead).
> 
> puts Airlines.AA # => "American Airlines"
> puts Airlines.BA # => "British Airways"
> 
> -Rich Kilmer
>