add_to_target

# File activerecord/lib/active_record/associations/collection_association.rb, line 281
      def add_to_target(record, skip_callbacks: false, replace: false, &block)
        if replace || association_scope.distinct_value
          index = @target.index(record)
        end
        replace_on_target(record, index, skip_callbacks, &block)
      end