HoneyHoney

修饰，是设计模式里面提到的，不影响原始的对象，给对象附上多个组件，让其能够支持多个方法。https://robots.thoughtbot.com/evaluating-alternative-decorator-implementations-in提到了几种方法，对比了一下，觉得SimpleDelegator还不错。对于简单的case，还可以直接用Forwardable。

相对于继承，修饰的好处是不需要像继承一样创建很多方法，直接就可以转到原始对象上去。

require 'delegate'

class Coffee
  def cost
    2
  end

  def origin
    "Colombia"
  end
end


module DecoratorClass
  def class
    __getobj__.class
  end
end

class Milk < SimpleDelegator
  include DecoratorClass

  def cost
    super + 0.4
  end
end

class Sugar < SimpleDelegator
  include DecoratorClass

  def cost
    super + 0.2
  end
end

p Milk.ancestors
coffee = Coffee.new
p Sugar.new(Milk.new(coffee)).cost   # 2.6
p Sugar.new(Sugar.new(coffee)).cost  # 2.4
p Milk.new(coffee).origin            # Colombia
p Sugar.new(Milk.new(coffee)).class  # Coffee