delete_or_destroy

# File activerecord/lib/active_record/associations/collection_association.rb, line 516
        def delete_or_destroy(records, method)
          records = records.flatten
          records.each { |record| raise_on_type_mismatch!(record) }
          existing_records = records.reject { |r| r.new_record? }

          if existing_records.empty?
            remove_records(existing_records, records, method)
          else
            transaction { remove_records(existing_records, records, method) }
          end
        end