Question

我正在努力学习无形。我有一个玩具项目，但我遇到了一个问题。

sealed trait RunnerType
object RunnerType {
  case object BasicRunner extends RunnerType
  case object MidComplex extends RunnerType
  case object ComplexRunner extends RunnerType
}
trait Runner[Input, Output] {
  type T
  def inner: Input => Output
  def apply(in: Input): Output = inner(in)
} 
object Runner { 
  case class A(inner: Int => String) extends Runner[Int, String] {
    type T = RunnerType.BasicRunner.type
  }  
  case class B(inner: Any => Any) extends Runner[Any, Any] {
    type T = RunnerType.MidComplex.type
  } 
  case class C(inner: String => (Int => String)) extends Runner[String, (Int => String)] {
    type T = RunnerType.BasicRunner.type
  } 
  //DSL
  def a(f: Int => String) = A(f) 
  def b(f: Any => Any) = B(f) 
  def c(f: String => (Int => String)) = C(f)
 // ops...
  val list = List(
    a(i => i.toString), 
    c(i => a => i.toString + (a + 10).toString)
    , b(a => a)
  )      
}

正如您所看到的，我的dsl不适合使用，因为我丢失了完全类型，我想通过RunnerType搜索。如果我使用HList，可能我可以保留类型信息。如“

  val hlist = 
    a(i => i.toString) ::: c(i => a => i.toString + (a + 10).toString) ::: b(a => a) ::: HNil

现在我想要一个方法，它将RunnerType作为参数，并返回正确的对象，我可以使用apply方法并知道输入和输出类型。例如：

  def lookup[L <: HList](t:RunnerType, hlist: L): Runner[correct_input, correct_output] = // Lookup in hlist for t(runner type)

是否正确使用Hlist？如果是的话，我怎么能用shapeess达到这个目标？

通过路径依赖类型从HList获取结果

0 个答案: