rails concern

concern.rb

require 'active_support/concern'

module Foo
  extend ActiveSupport::Concern
  included do
    p self
    def self.do_host_something
      :do_host_something
    end
  end 
end

module Bar
  extend ActiveSupport::Concern
  include Foo
  included do 
    self.send(:do_host_something)
  end
end

class Host
  include Bar
end