“扩展自我”是否与“模块功能”相同?

module_function 将给定的实例方法设为私有,然后复制并将它们作为公共方法放入模块的元类中。 extend self 将所有实例方法添加到模块的singleton中,使其可见性保持不变。

module M
  extend self

  def a; end

  private
  def b; end
end

module N
  def c; end

  private
  def d; end

  module_function :c, :d
end

class O
  include M
  include N
end

M.a
M.b  # NoMethodError: private method `b' called for M:Module
N.c
N.d
O.new.a
O.new.b  # NoMethodError: private method `b' called for O
O.new.c  # NoMethodError: private method `c' called for O
O.new.d  # NoMethodError: private method `d' called for O