模块中的实例变量? [英] Instance variables in modules?

问题描述

即使无法创建模块的实例，怎么可能在模块中包含实例变量?以下模块Stacklike中@stack的用途是什么?

How is it possible that I can have instance variables in a module even though I cannot create an instance of the module? What would be the purpose of @stack in module Stacklike below?

module Stacklike
  def stack
    @stack ||= []
  end
end

推荐答案

将实例变量视为在包含您的模块的任何类中都将存在的东西，并且事情变得更有意义了:

Think of the instance variable as something which will exist in any class that includes your module, and things make a bit more sense:

module Stacklike
  def stack
    @stack ||= []
  end

  def add_to_stack(obj)
    stack.push(obj)
  end

  def take_from_stack
    stack.pop
  end
end

class ClownStack
  include Stacklike

  def size
    @stack.length
  end
end

cs = ClownStack.new
cs.add_to_stack(1)
puts cs.size

将输出"1"

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