clyfe.rb

require "active_support"

class FooOne
  def m; 1; end
end

class FooTwo # classy
  def m; 1; end
end

puts FooOne.new.m #=> 1

module Bar
  def m; 42; end
end

module Baz
  def m; 42; end
end

# Monkey-patching!
module Bar
  extend ActiveSupport::Concern

  included do
    alias_method :m_old, :m
    def m; m_old + 1; end
  end
end

class FooOne; include Bar; end

puts FooOne.new.m #=> 2

module Baz
  extend ActiveSupport::Concern

  included do
    alias_method :m_oldish, :m
    def m; m_oldish + 1; end
  end
end

class FooTwo; include Bar; include Baz; end

puts FooTwo.new.m #=> 3