override methods through eigenclass

override methods through eigenclass.rb

class Greeter
  def greet
    "hello"
  end
end

module ItalianGreeter
  def greet
    "ciao"
  end
end

module ReverseGreeter
  def greet
    super.reverse
  end
end

g = Greeter.new
puts g.greet #=> hello

g.extend ItalianGreeter
puts g.greet #=> ciao

g.extend ReverseGreeter
puts g.greet #=> oaic