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scala - 如何在scala中实现类型安全域存储库?

转载 作者:行者123 更新时间:2023-12-02 09:07:49 32 4
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我想实现通用且类型安全的域存储库。说我有

trait Repo[Value] {
def put(value: Value): Unit
}

case class IntRepo extends Repo[Int] {
override def put(value: Int): Unit = ???
}

case class StringRepo extends Repo[String] {
override def put(value: String): Unit = ???
}

case class DomainRepo(intRepo: IntRepo, stringRepo: StringRepo) {
def putAll[?](values: ?*): Unit // what type should be here?
}

因此我想要以下 api:

domainRepo.putAll(1, 2, 3, "foo", "bar") //Should work
domainRepo.putAll(1, 2, true, "foo") // should not compile because of boolean value

问题是如何实现这一目标?

所以,我只看到一种使其类型安全的方法。它是对任何类型进行模式匹配,例如

def putAll(values: Seq[Any]) => Unit = values.foreach {
case str: String => stringRepo.put(str)
case int: Int => intRepo.put(int)
case _ => throw RuntimeException // Ha-Ha
}

但是如果我这里有 10000 种类型怎么办?那会是一团糟!

目前我还不清楚的另一种方法是使用 dotty type | (或)如下所示:

type T = Int | String | 10000 other types // wouldn't be a mess?

def putAll(t: T*)(implicit r1: Repo[Int], r2: Repo[String] ...) {
val myTargetRepo = implicitly[Repo[T]] // would not work
}

所以,你觉得怎么样?这可能吗?

我见过的最简单的方法是

Map[Class[_], Repo[_]]

但是这种方式可能会犯很多错误

最佳答案

您似乎正在寻找类型类

trait Repo[Value] {
def put(value: Value): Unit
}

implicit val intRepo: Repo[Int] = new Repo[Int] {
override def put(value: Int): Unit = ???
}

implicit val stringRepo: Repo[String] = new Repo[String] {
override def put(value: String): Unit = ???
}

case object DomainRepo {
def putAll[Value](value: Value)(implicit repo: Repo[Value]): Unit = repo.put(value)
}

如果您希望 domainRepo.putAll(1, 2, 3, "foo", "bar") 编译并 domainRepo.putAll(1, 2, true, "foo")无法编译,可以尝试使用异构集合(HList)。

import shapeless.{HList, HNil, ::, Poly1}
import shapeless.ops.hlist.Mapper

trait Repo[Value] {
def put(value: Value): Unit
}

implicit val intRepo: Repo[Int] = new Repo[Int] {
override def put(value: Int): Unit = ???
}

implicit val stringRepo: Repo[String] = new Repo[String] {
override def put(value: String): Unit = ???
}

case object DomainRepo {
def put[Value](value: Value)(implicit repo: Repo[Value]): Unit = repo.put(value)

object putPoly extends Poly1 {
implicit def cse[Value: Repo]: Case.Aux[Value, Unit] = at(put(_))
}

def putAll[Values <: HList](values: Values)(implicit
mapper: Mapper[putPoly.type, Values]): Unit = mapper(values)
}

DomainRepo.putAll(1 :: 2 :: 3 :: "foo" :: "bar" :: HNil)
// DomainRepo.putAll(1 :: 2 :: true :: "foo" :: HNil) // doesn't compile

关于scala - 如何在scala中实现类型安全域存储库?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/55942894/

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