ruby-on-rails – 一次验证单独案例的最小和最大长度

validates :surname,:presence       => true,:length         => { :within => min_surname_length..max_surname_length,:message => "is bad (minimum is #{min_surname_length},maximum is  is #{max_surname_length})" }

但是我希望在没有单独语法验证的情况下将最小值和最大值分开

validates_length_of :name,:minimum => 3
validates_length_of :name,:maximum => 30

简而言之,我想做这样的事情(我知道,这是错的)：

validates :surname,:message => "is bad (minimum is #{min_surname_length}" IF MINIMUM,:message => "is bad (maximum is  is #{max_surname_length})" IF MAXIMUM }

怎么可能一次做到这一点？

解

这是我将如何使用它：

validates :surname,:length         => { :within => min_password_length..max_password_length,:too_short => 'too short message',:too_long => 'too long message' }