Ruby重写运算符

class MyObject
  cattr_accessor :value_     # Note the `cattr_accessor` as opposed to `attr_accessor`.

  def +(right_)
    self.value_ + right_.value_
  end
end

x = MyObject.new
y = MyObject.new

x.value_ = 1
y.value_ = 2

puts x + y

但它不起作用。