Ruby on Rails Password Validation

Question

So I have interesting password validation requirements:

• When a user signs up, I want them to have to type in password and confirm and be between 6..4

Answer 1

this works for blank password on update action:

validates :password, :presence => true, :on => :update,
 :if => lambda{ !password.nil? }

validates :password,
  :confirmation => true,
  :length => { :minimum => 6},
  :if => lambda{ new_record? || !password.nil? }