Question

在下面的例子中，我得到找不到参数zipper的隐含值：shapeless.ops.hlist.Zip [shapeless。:: [keys.Out，shapeless。:: [mapper.Out，shapeless。高抗扰度逻辑]]]

我认为我需要另一个隐含的，但无法解决语法问题。想法？

def mapCCLV[P <: Product, K <: HList, L <: HList, M <: HList](p: P)(poly: Poly1)(
    implicit gen: Generic.Aux[P, L], lab: LabelledGeneric.Aux[P, K], 
    keys: Keys[K], mapper: Mapper.Aux[poly.type, L, M]) = {
  val k = keys.apply
  val v = gen.to(p).map(poly)
  k.zip(v)
}

Answer 1

与错误消息一样，您需要为var today = DateTime.Now; var activeMembers = allMembers.Where(m => m.Memberships.Any(ms => ms.Status == "Active" && (ms.StartDate == null || ms.StartDate <= today) && (ms.EndDate == null || today <= ms.EndDate)));类型类实例提供额外的隐式参数，以便能够压缩。

Zip

您更有可能想要使用import shapeless._, shapeless.ops.hlist._, record._, ops.record._, labelled._ def mapCCLV[P <: Product, LG <: HList, K <: HList, G <: HList, M <: HList]( p: P)(poly: Poly1 )(implicit gen: Generic.Aux[P, G], lab: LabelledGeneric.Aux[P, LG], keys: Keys.Aux[LG, K], mapper: Mapper.Aux[poly.type, G, M], zip: Zip[K :: M :: HNil] ): zip.Out = { val k = keys() val v = gen.to(p).map(poly) k.zip(v) }代替ZipWithKeys。

Zip

Scala无形拉链问题

1 个答案: