construct

# File activerecord/lib/active_record/associations/join_dependency.rb, line 155
      def construct(parent, associations, join_parts, row)
        case associations
        when Symbol, String
          name = associations.to_s

          join_part = join_parts.detect { |j|
            j.reflection.name.to_s == name &&
              j.parent_table_name == parent.class.table_name }

            raise(ConfigurationError, "No such association") unless join_part

            join_parts.delete(join_part)
            construct_association(parent, join_part, row)
        when Array
          associations.each do |association|
            construct(parent, association, join_parts, row)
          end
        when Hash
          associations.sort_by { |k,_| k.to_s }.each do |association_name, assoc|
            association = construct(parent, association_name, join_parts, row)
            construct(association, assoc, join_parts, row) if association
          end
        else
          raise ConfigurationError, associations.inspect
        end
      end