A lightweight, very convenient function to dynamically create good enums in Ruby

enum.rb

# Makes an enum class whose instances are all constants with uppercase names,
# but whose case of string representations are customizable. For example,
# Color = make_enum_class('red', 'amber', 'green') returns the class Color
# with members Color::RED, Color::AMBER, and Color::GREEN. The to_s methods
# produce 'red', 'green', and 'blue', respectively. To get the instance
# from the string, use, for example, Color.from_string('blue'), which will
# return Color.BLUE.

def make_enum_class(*constants)
  cap = ->(s){s.upcase.gsub(/ /, '_')}
  cls = Class.new
  constants.each do |name|
    cls.const_set(cap[name], cls.new).define_singleton_method(:to_s) {name}
  end
  cls.define_singleton_method(:from_s) {|s| cls.const_get(cap[s]) rescue nil}
  cls
end