Using Module Prepend To Extend Ruby Classes

prepend.rb

class Foo
  attr_reader :bar
  def initialize
    @bar = 'bar'
  end
end

module Bar
  def bar
    super.upcase
  end
end

Foo.prepend Bar
Foo.new.bar # => 'BAR'

# If include was used:
Foo.include Bar
Foo.new.bar # => 'bar'