Ruby 重新使用被覆盖的方法

class Pet
  def play
    'Pet play'
  end
end

class Dog < Pet
  def play
    'Dog play'
  end
end

Dog 重写了 play 方法, 方法查找时, 会优先找到 Dog#play .

对于 Dog 的对象, 他就永远看不到 Pet#play, 不过还是有办法来实现:

puts Dog.new.play
# => Dog play

Dog.define_method(:play, Pet.instance_method(:play))

puts Dog.new.play
# => Pet play

或者影响更小的方法:

dog = Dog.new
dog.define_singleton_method(:play, Pet.instance_method(:play))
puts dog.play
# => Pet play

puts Dog.new.play
# => Dog play