save_belongs_to_association

# File activerecord/lib/active_record/autosave_association.rb, line 400
    def save_belongs_to_association(reflection)
      association = association_instance_get(reflection.name)
      record      = association && association.load_target
      if record && !record.destroyed?
        autosave = reflection.options[:autosave]

        if autosave && record.marked_for_destruction?
          record.destroy
        elsif autosave != false
          saved = record.save(:validate => !autosave) if record.new_record? || (autosave && record.changed_for_autosave?)

          if association.updated?
            association_id = record.send(reflection.options[:primary_key] || :id)
            self[reflection.foreign_key] = association_id
            association.loaded!
          end

          saved if autosave
        end
      end
    end