class EnvironmentSerializer < BaseSerializer include WithPagination Item = Struct.new(:name, :size, :latest) entity EnvironmentEntity def within_folders tap { @itemize = true } end def itemized? @itemize end def represent(resource, opts = {}) if itemized? itemize(resource).map do |item| { name: item.name, size: item.size, latest: super(item.latest, opts) } end else super(resource, opts) end end private def itemize(resource) items = resource.order('folder ASC') .group('COALESCE(environment_type, name)') .select('COALESCE(environment_type, name) AS folder', 'COUNT(*) AS size', 'MAX(id) AS last_id') # It makes a difference when you call `paginate` method, because # although `page` is effective at the end, it calls counting methods # immediately. items = @paginator.paginate(items) if paginated? environments = resource.where(id: items.map(&:last_id)).index_by(&:id) items.map do |item| Item.new(item.folder, item.size, environments[item.last_id]) end end end