Scope chain

# encoding: utf-8
 
#####################
# The Example Class #
#####################
 
class Example
  def self.execute(&block)
    class_eval(&block)
  end
 
  def self.some_code(&block)
    new.instance_eval(&block)
  end
end
 
#####################
# Object Extensions #
#####################
 
module ObjectExtensions
  def execute(&block)
    Example.execute(&block)
  end
end
 
###################################
# Instance Extensions for Example #
###################################
 
module ExampleInstanceExtensions
  def one
    'one'
  end
 
  def two
    'two'
  end
 
  def three
    'three'
  end
end
 
########################
# Macroses for Example #
########################
 
module ExampleClassExtensions
  def do_one
    some_code do
      "do #{one}"
    end
  end
 
  def do_two
    some_code do
      "do #{two}"
    end
  end
 
  def do_three
    some_code do
      "do #{three}"
    end
  end
 
  def the_macros
    yield
  end
end
 
Object.__send__(:include, ObjectExtensions)
Example.__send__(:extend, ExampleClassExtensions)
Example.__send__(:include, ExampleInstanceExtensions)
 
#####################
# The Demonstration #
#####################
 
puts "The #{self} scope." #=> main
 
some_code rescue puts 'some_code boom!' #=> some_code boom!
one       rescue puts 'one boom!'       #=> one boom!
two       rescue puts 'two boom!'       #=> two boom!
three     rescue puts 'three boom!'     #=> three boom!
 
execute do
  the_macros do
    puts "The #{self} scope." #=> the Example class
    puts do_one,  #=> do one
         do_two,  #=> do two
         do_three #=> do three
  end
 
  some_code do
    puts "The #{self} scope." #=> an Example instance
    puts one,  #=> one
         two,  #=> two
         three #=> three
  end
 
  execute do
    some_code do
      puts "The #{self} scope." #=> an Example instance.
      puts one,  #=> one
           two,  #=> two
           three #=> three
    end
  end
 
  puts "The #{self} scope." #=> the Example class
  one   rescue puts 'one again boom!'   #=> one again boom!
  two   rescue puts 'two again boom!'   #=> two again boom!
  three rescue puts 'three again boom!' #=> three again boom!
end