decorator_example.rb

class DecoratorExample
  
  # Add functionality to a method.
  def self.my_decorator method
    imeth = instance_method method
    define_method method do |*args, &block|
      "does stuff to " +
        imeth.bind(self).call(*args, &block)
    end
  end
  
  # Returns a description of itself.
  my_decorator def foo
    'the foo method'
  end
  
end

d = DecoratorExample.new
puts d.foo
# => does stuff to the foo method

require 'pry'; binding.pry