如何在Ruby / Rails中抽象与父类相似的验证/关系？

class DeliveryDocument < CommercialDocument
  # Relations
  belongs_to :biller, :class_name => \'Company\'
  belongs_to :customer, :class_name => \'Company\'
  belongs_to :customer_center, :class_name => \'Center\'
  has_many :delivery_document_lines, :dependent => :destroy
  alias_attribute :lines, :delivery_document_lines
  # Some configuration
  accepts_nested_attributes_for :delivery_document_lines
  acts_as_freezable :only_dependencies => true,
    :has_many => [:delivery_document_lines],
    :belongs_to => [:biller, :customer, :customer_center]
  acts_as_clonable :has_many => [:delivery_document_lines]
  validates_each :lines do |record, attr, value|
    # ...
  end
end

class InvoiceDocument < CommercialDocument
  self.
  # Relations
  belongs_to :biller, :class_name => \'Company\'
  belongs_to :customer, :class_name => \'Company\'
  belongs_to :customer_center, :class_name => \'Center\'
  has_many :invoice_document_lines, :dependent => :destroy
  alias_attribute :lines, :invoice_document_lines
  # Some configuration
  accepts_nested_attributes_for :invoice_document_lines
  acts_as_freezable :only_dependencies => true,
    :has_many => [:invoice_document_lines],
    :belongs_to => [:biller, :customer, :customer_center]
  acts_as_clonable :has_many => [:invoice_document_lines]
  # Validations
  validates_each :lines do |record, attr, value|
    # ...
  end
end

class CommercialDocument < Document  # document inherits from AR::Base
  # ...
  has_many :\"#{self.to_s.underscore}_lines\", :dependent => :destroy
  # ...
  accepts_nested_attributes_for :\"#{self.to_s.underscore}_lines\"
  # ...
end

self.to_s

CommercialDocument