alias_attribute

class Person
  include ActiveModel::AttributeMethods

  attr_accessor :name
  attribute_method_suffix '_short?'
  define_attribute_methods :name

  alias_attribute :nickname, :name

  private

  def attribute_short?(attr)
    send(attr).length < 5
  end
end

person = Person.new
person.name = 'Bob'
person.name            # => "Bob"
person.nickname        # => "Bob"
person.name_short?     # => true
person.nickname_short? # => true