ruby singletons

# rb singletons
# idea from http://ozmm.org/posts/singin_singletons.html

# using the 'extend self' technique to treat a 
# module like a singleton class. note:
# module now behaves like a class but
# since it is not a class you cannot create a new 
# instance
module SelfTest
  extend self
  def test
    puts "#{self.ancestors.first} test called"
  end
end

# using standard self.method_name
# works like extend self example except you 
# have to specify self when defining method but
# you can still create instances with new
class ClassMethodTest
  def self.test
   puts "#{self.ancestors.first} test called"
  end
end

require 'singleton' # need to require this
# including Singleton undefines new
# to deter the creation of instances
class SingletonTest
  include Singleton
  def test
    puts "#{self.class} test called"
  end
end

if __FILE__ == $0 
  SelfTest.test
  ClassMethodTest.test
  SingletonTest.instance.test
end