From: Patrick Hurley <phurley@...>
Date: 2005-08-03T04:32:22+09:00
Subject: Re: enum collection of constant values

On 8/2/05, Ara.T.Howard <Ara.T.Howard@noaa.gov> wrote:
> On Wed, 3 Aug 2005, Garance A Drosehn wrote:
> > I'd like to have a set of constants for a class, where their values
> > need to be unique, and preferably compact.  For instance:
> class methods are your friend
> 
> snip nice Enum module

I like the Enum module, but if I include it into the 'main' scope, I need to 

self.class.enum to make it work. A bit more brute force, but works
"automatically" in all contexts would be overloading Object. This then
requires a smarter method of setting the const based upon where it is
called from.

class Object

  def const_setter
    set = if self.respond_to? :const_set
      lambda { |sym, val| self.const_set sym.to_s.intern, val }
    elsif self.class.respond_to? :const_set
      lambda { |sym, val| self.class.const_set sym.to_s.intern, val }
    else
      # I don't think this code would ever get called...
      lambda { |sym, val| eval "#{sym} = #{val}" }
    end
  end

  def enum(*syms)
    set = const_setter
    syms.each_with_index do |sym,index|
      set.call sym, index
    end
  end

  def binary_enum(*syms)
    set = const_setter
    syms.each_with_index do |sym,index|
      set.call sym, 2 ** index
    end
  end

end