在另一个模块中扩展 Ruby 模块，包括模块方法 [英] Extending a Ruby module in another module, including the module methods

问题描述

每当我尝试扩展 ruby​​ 模块时，我都会丢失模块方法.include 和 extend 都不会这样做.考虑片段:

Whenever I try to extend a ruby module, I lose the module methods. Neither include nor extend will do this. Consider the snippet:

module A 
  def self.say_hi
    puts "hi"
  end
end

module B 
  include A
end

B.say_hi  #undefined_method

无论 B 包含还是扩展 A，say_hi 都不会被定义.

Whether B Includes or Extends A, say_hi will not be defined.

有没有办法完成这样的事情?

Is there any way to accomplish something like this?

推荐答案

如果你是 module A 的作者并且经常需要这个，你可以像这样重新创作 A:

If you are the author of module A and will frequently need this, you can re-author A like so:

module A 
  module ClassMethods
    def say_hi
      puts "hi"
    end
  end
  extend ClassMethods
  def self.included( other )
    other.extend( ClassMethods )
  end
end

module B 
  include A
end

A.say_hi #=> "hi"
B.say_hi #=> "hi" 

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