Ruby自定义类重写<=>比较运算符

看一下<=>的行为，
前面大返回 1 后面大返回 -1 相等返回 0

>> 1 <=> 2
=> -1
>> 2 <=> 1
=> 1
>> 1 <=> 1
=> 0

自定义类

class Compare

  attr_accessor :date
  def initialize(date)
    @date = date
  end
  
  # 按照日期倒序排列
  def <=>(other_compare)
    other_compare.date <=> self.date
  end

end