endendmoduleHelperMethods# Validates that the specified attributes are blank (as defined by# Object#blank?). Happens by default on save.## class Person < ActiveRecord::Base# validates_absence_of :first_name# end## The first_name attribute must be in the object and it must be blank.## Configuration options:# * <tt>:message</tt> - A custom error message (default is: "must be blank").## There is also a list of default options supported by every validator:# +:if+, +:unless+, +:on+ and +:strict+.# See <tt>ActiveModel::Validation#validates</tt> for more informationdefvalidates_absence_of(*attr_names)validates_withAbsenceValidator,_merge_attributes(attr_names)endendendend