configure_dependency_for_has_one

# File activerecord/lib/active_record/associations.rb, line 1653
        def configure_dependency_for_has_one(reflection)
          if reflection.options.include?(:dependent)
            name = reflection.options[:dependent]
            method_name = :"has_one_dependent_#{name}_for_#{reflection.name}"

            case name
              when :destroy, :delete
                class_eval                   def #{method_name}                    association = #{reflection.name}                    association.#{name} if association                  end, __FILE__, __LINE__ + 1
              when :nullify
                class_eval                   def #{method_name}                    association = #{reflection.name}                    association.update_attribute(#{reflection.primary_key_name.inspect}, nil) if association                  end, __FILE__, __LINE__ + 1
              when :restrict
                method_name = "has_one_dependent_restrict_for_#{reflection.name}".to_sym
                define_method(method_name) do
                  unless send(reflection.name).nil?
                    raise DeleteRestrictionError.new(reflection)
                  end
                end
                before_destroy method_name
              else
                raise ArgumentError, "The :dependent option expects either :destroy, :delete, :nullify or :restrict (#{reflection.options[:dependent].inspect})"
            end

            before_destroy method_name
          end
        end