class ActiveRecord::Associations::Builder::Association

def configure_dependency
  unless valid_dependent_options.include? options[:dependent]
    raise ArgumentError, "The :dependent option must be one of #{valid_dependent_options}, but is :#{options[:dependent]}"
  end
  if options[:dependent] == :restrict
    ActiveSupport::Deprecation.warn(
      "The :restrict option is deprecated. Please use :restrict_with_exception instead, which " \
      "provides the same functionality."
    )
  end
  mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
    def #{macro}_dependent_for_#{name}
      association(:#{name}).handle_dependency
    end
  CODE
  model.before_destroy "#{macro}_dependent_for_#{name}"
end