create_through_record

# File activerecord/lib/active_record/associations/has_one_through_association.rb, line 15
        def create_through_record(record, save)
          ensure_not_nested

          through_proxy  = through_association
          through_record = through_proxy.load_target

          if through_record && !record
            through_record.destroy
          elsif record
            attributes = construct_join_attributes(record)

            if through_record && through_record.destroyed?
              through_record = through_proxy.tap(&:reload).target
            end

            if through_record
              if through_record.new_record?
                through_record.assign_attributes(attributes)
              else
                through_record.update(attributes)
              end
            elsif owner.new_record? || !save
              through_proxy.build(attributes)
            else
              through_proxy.create(attributes)
            end
          end
        end