Entity model for entities to inherit

entity.rb

class Entity
  include ActiveModel::Validations
  attr_accessor :id

  def self.attr_accessor(*vars)
    @class_attributes ||= [:id]
    @class_attributes.concat vars
    super(*vars)
  end

  def self.class_attributes
    @class_attributes
  end

  def self.inherited(sublass)
    sublass.attr_accessor(*@class_attributes)
  end

  def initialize(attr = {})
    attr.each do |name, value|
      send("#{name}=", value)
    end
  end
end