replace

# File activerecord/lib/active_record/associations/collection_association.rb, line 240
      def replace(other_array)
        other_array.each { |val| raise_on_type_mismatch!(val) }
        original_target = load_target.dup

        if owner.new_record?
          replace_records(other_array, original_target)
        else
          replace_common_records_in_memory(other_array, original_target)
          if other_array != original_target
            transaction { replace_records(other_array, original_target) }
          else
            other_array
          end
        end
      end