Ruby on rails 多态Ruby SimpleLegator

除了

SimpleDelegator

之外，还有哪些方法可以利用多态性而不修改底层对象

这是一个示例，

SimpleLegator

无法解决的问题

其目的是能够将原始对象（

delicious\u food

）与任何其他（

yak\u food

）包装在一起，以便替代方法（

delicious？

）取决于基础对象的非替代方法

class Food
  def initialize(color)
    @color = color
  end

  def delicious?
    color == :red
  end

  def color
    @color
  end
end

class FoodTasteOverride < SimpleDelegator
  def color
    :green
  end
end

delicious_food = Food.new(:red)
yak_food = FoodTasteOverride.new delicious_food

delicious_food.delicious? # true - expected
yak_food.delicious? # expecting false, but is true since the color come from delicious_food

---

另一种方法是使用extend扩展实例的方法。（这是大多数DCI实现在运行时通过行为扩展对象所做的）

---

在这种情况下使用模块对我来说也更合理。装饰师不应该改变内部结构。好主意。出于某种原因，没有考虑扩展。

yak_food = delicious_food.clone
def yak_food.color
  :green
end

class Food

  attr_reader :color

  def initialize(color)
    @color = color
  end

  def delicious?
    self.color == :red
  end

end

module FoodTasteOverride
  def color
    :green
  end
end


normal_food = Food.new(:red)
delicious_food = Food.new(:red)
yak_food = normal_food.extend(FoodTasteOverride)

puts delicious_food.delicious? # true - expected
puts yak_food.delicious? #false because the color is now green.