如何在scala中显示一个HList的类型无形

Question

如何将HList的类型作为String获取,以便我可以打印它.例如"Int :: Long :: String :: HNil"

val gen = Generic[?]
val typeString: String = ???
println("The type is " + typeString)

我知道它的字符串不是很有用,通常你想要的类型 gen.Repr

Answer 1

用途shapeless.Typeable:

scala> import shapeless._
import shapeless._

scala> case class A(i: Int, s: String)
defined class A

scala> val gen = Generic[A]
gen: shapeless.Generic[A]{type Repr =
  shapeless.::[Int,shapeless.::[String,shapeless.HNil]]} =
    anon$macro$14$1@56639061

scala> println(Typeable[gen.Repr].describe)
Int :: String :: HNil