def_and_class_as_methods.rb

require 'rubygems'
require 'activesupport'

class Object
  
  # As popularized by Why:
  # http://whytheluckystiff.net/articles/seeingMetaclassesClearly.html
  #
  def metaclass
    class << self; return self; end
  end
  
  # Let's def def.
  #
  def def name, &block
    metaclass.send :define_method, name, &block
  end
  
  # Finally, the ability to define new classes.
  # Note: See the end of the article for API ideas.
  #
  def class name, superclass = Object, namespace = '', &block
    namespace.to_s.constantize.const_set name, Class.new(superclass, &block)
  end
  
end

class Class
  
  # Let's install a convenience method that is installed
  # on all instances of this Class.
  #
  def def_on_all_instances name, &block
    send :define_method, name, &block
  end
  
end

# Let's see how we would use def on a Class.
#
Monkey = Class.new
Monkey.def :interests do
   "Monkeys love bananas, and tightly coupled code."
end
puts Monkey.interests

# Let's see how we would use def on a single instance.
#
m = Monkey.new
m.def :demonstrate do
  "The monkey tries to run his code. And fails."
end
puts m.demonstrate

# This monkey cannot demonstrate.
#
n = Monkey.new
puts "Well, could his younger brother demonstrate? #{n.respond_to?(:demonstrate) ? 'Yes.' : 'No. Only older brother monkey can.' }"

# Let's define a method for all instances Monkey has produced and will produce.
#
Monkey.def_on_all_instances :sulk do
  "Monkey is sulking. Well, monkey, if you just would listen and decouple your code!"
end
puts m.sulk
puts Monkey.new.sulk # So, all monkeys know how to sulk.

# How about class?
#
self.class :Chimp do
  def self.skreech
    puts 'Eeek!'
  end
end
Chimp.skreech

# And namespacing?
#
Apes = Module.new
self.class :Chimp, Object, :Apes do
  def self.skreech
    puts 'Eeek!'
  end
end
Apes::Chimp.skreech

# How about subclassing?
#
self.class :ArraySubclass, Array  do
end
puts ArraySubclass.superclass


# API idea
# self.class 'Apes::Chimp', Apes::Base do
#   ...
# end