scala – 如何使用Kleisli实现缓存

所以所有的服务方法都归功于Kleisli.

问题是如何在这些服务上添加可更新缓存.

这是我目前的实现,有更好的方法(现有组合器,更多功能方法,……)？

import scala.concurrent.duration.Duration
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.{Await,Future}
import scalaz.Kleisli

trait Repository {
  def all : Future[Seq[String]]
  def replaceAll(l: Seq[String]) : Future[Unit]
}

trait Service {
  def all = Kleisli[Future,Repository,Seq[String]] { _.all }
  def replaceAll(l: Seq[String]) = Kleisli[Future,Unit] { _.replaceAll(l) }
}

trait CacheService extends Service {
  var cache : Seq[String] = Seq.empty[String]

  override def all = Kleisli[Future,Seq[String]] { repo: Repository =>
    if (cache.isEmpty) {
      val fcache = repo.all
      fcache.foreach(cache = _)
      fcache
    }
      else
      Future.successful(cache)
  }

  override def replaceAll(l: Seq[String]) = Kleisli[Future,Unit] { repo: Repository =>
    cache = l
    repo.replaceAll(l)
  }
}

object CacheTest extends App {
  val repo = new Repository {
    override def replaceAll(l: Seq[String]): Future[Unit] = Future.successful()
    override def all: Future[Seq[String]] = Future.successful(Seq("1","2","3"))
  }
  val service = new CacheService {}

  println(Await.result(service.all(repo),Duration.Inf))
  Await.result(service.replaceAll(List("a"))(repo),Duration.Inf)
  println(Await.result(service.all(repo),Duration.Inf))
}

[更新]关于@timotyperigo的评论,我在存储库级别实现了缓存

class CachedTipRepository(val self:TipRepository) extends TipRepository {
  var cache: Seq[Tip] = Seq.empty[Tip]

  override def all: Future[Seq[Tip]] = …

  override def replace(tips: String): Unit = …
}

我仍然对改进设计的反馈感兴趣.