meta_self.rb

class Person
  def self.person 
    "Person"
  end
end

class Person
  class << self
    def hello
      "Hello"
    end
  end
end

class << Person
  def hi
    "Hi"
  end
end

Person.instance_eval  do
  def morning
    "Morning"
  end
end

def Person.evening
  "Evening"
end

puts Person.person
puts Person.hello
puts Person.hi
puts Person.morning
puts Person.evening

class Person
  def name
    "Name"
  end
end

Person.class_eval do
  def age
    "Age"
  end
end

puts "Person.new.inspect: #{Person.new.inspect}"
puts "Person.new.class.inspect: #{Person.new.class.inspect}"
puts "Person.new.name :#{Person.new.name}"
puts "Person.new.age: #{Person.new.age}"


puts "*" * 50

class MetaSelf; end
puts "MetaSelf.class: #{MetaSelf.class}"
puts "MetaSelf.superclass: #{MetaSelf.superclass}"
puts "MetaSelf.class.superclass: #{MetaSelf.class.superclass}"

class Class
  def loud_name
    "#{name.upcase}"
  end  
end

puts "MetaSelf.loud_name: #{MetaSelf.loud_name}"
puts "Person.loud_name: #{Person.loud_name}"


puts "*" * 50


matz = Object.new
def matz.speak
  "who is matz ?"
end

puts "matz.inspect: #{matz.inspect}"
puts "matz.speak: #{matz.speak}"

puts "*" * 50

metaclass = class << matz; self; end
puts "metaclass.instance_methods: #{metaclass.instance_methods}"
puts "metaclass.instance_methods.grep(/speak/): #{metaclass.instance_methods.grep(/speak/)}"
  
puts "*" * 50

class MetaSelf
  def name
    "MetaSelf's name"
  end
end  

puts MetaSelf.name
puts MetaSelf.new.name

MetaSelf.class_eval do
  def meta
    "Meta"    
  end
end

puts MetaSelf.new.meta

ruby-metaprogramming.rb

class MailTruck
  attr_accessor :driver, :route
  
  def initialize(driver, route)
    @driver = driver
    @route = route
  end
  
  
end


m = MailTruck.new("Harold", ["12 Zhongshan Way", "34 South Street"])
puts m.inspect
puts m.class

m.instance_variable_set("@speed", 45)
puts m.instance_variable_get('@speed')

puts m.inspect
puts m.object_id
puts MailTruck.object_id


require 'yaml'
class << m
  def to_yaml_properties
    ['@driver', '@route']
  end
end
 
puts YAML::dump m

sing = 
class << self
  self 
end 

puts sing.inspect


class Class
  def attr_abort(*args)
    abort "Please no more attributes today"
  end
end

class MetaRuby
  attr_abort :id, :name, :age
end



http://yehudakatz.com/2009/11/15/metaprogramming-in-ruby-its-all-about-the-self/
http://ruby-metaprogramming.rubylearning.com/
http://viewsourcecode.org/why/hacking/seeingMetaclassesClearly.html