construct_association

# File activerecord/lib/active_record/associations/join_dependency.rb, line 203
      def construct_association(record, join_part, row)
        return if record.id.to_s != join_part.parent.record_id(row).to_s

        macro = join_part.reflection.macro
        if macro == :has_one
          return record.association(join_part.reflection.name).target if record.association_cache.key?(join_part.reflection.name)
          association = join_part.instantiate(row) unless row[join_part.aliased_primary_key].nil?
          set_target_and_inverse(join_part, association, record)
        else
          association = join_part.instantiate(row) unless row[join_part.aliased_primary_key].nil?
          case macro
          when :has_many, :has_and_belongs_to_many
            other = record.association(join_part.reflection.name)
            other.loaded!
            other.target.push(association) if association
            other.set_inverse_instance(association)
          when :belongs_to
            set_target_and_inverse(join_part, association, record)
          else
            raise ConfigurationError, "unknown macro: #{join_part.reflection.macro}"
          end
        end
        association
      end