extend == singleton include

test.rb

# extend == include in singleton class

module Mincluded
  def toto
    puts 'Mincluded#toto'
  end
end

module MSingletonIncluded
  def toto
    puts 'MSingletonIncluded#toto'
  end
end

module MExtended
  def toto
    puts 'MExtended#toto'
  end
end


class A
  include Mincluded
  extend MExtended
  class << self
    include MSingletonIncluded
  end
end

A.ancestors
A.singleton_class.ancestors

A.toto
A.new.toto


def A.new.pouet
  puts 'pouet'
end