是“自我扩展"吗?与"module_function"相同吗?

问题描述

extend self和module_function是制作它的两种方法，因此您可以调用模块上的方法，如果包含该模块，也可以调用它.

extend self and module_function are two ruby ways to make it so you can call a method on a module and also call it if you include that module.

这些方式的最终结果之间有什么区别吗?

Are there any differences between the end results of those ways?

推荐答案

module_function将给定的实例方法设为私有，然后进行复制并将其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单例中，而使其可见性保持不变.

module_function makes the given instance methods private, then duplicates and puts them into the module's metaclass as public methods. extend self adds all instance methods to the module's singleton, leaving their visibilities unchanged.

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

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