在Scala中分解函数

Question

所以我有以下函数定义。

def partition[A, B, C](
    partitionF: A => Either[B, C])

其中A，B和C是任意类型。

现在，我正在定义要传递的函数

sealed trait Response
case object ThisResponse extends Response
case object ThatResponse extends Response

case object ThisDirection
case object ThatDirection

def responsePartition(response: Response): 
    Either[ThisDirection, ThatDirection] = response match {
  case ThisResponse => Left(ThisDirection)
  case ThatResponse => Right(ThatDirection)
}

然后我们将其传递如下

partition(responsePartition)

在业务逻辑中。

现在，我试图单独获取responsePartition中定义的A => B和A => C方法

所以我要找的是

val partitionFonB : A => B = ??? // This is case of this example would be ThisResponse => ThisDirection

和

val partitionFonC : A => C = ??? // This is case of this example would be ThatResponse => ThatDirection

有没有办法做到这一点？我尝试过向右投影和向左投影，但是我无法获得正确的类型。

Answer 1

通常，您不能从type的函数中提取（总计）A => B或A => C函数A => Either[B, C]。如果该函数B为特定值生成一个a1，A => C则不会在此处定义该函数，反之亦然。

如果您所拥有的A => Either[B, C]只是A => Option[B]and A => Option[C]（使用_.toLeft.toOptionand _.toOption），那么您将尽力而为。

对于您的特殊情况，您可以提取ThisResponse => ThisDirection和ThatResponse => ThatDirection作为单独的函数开始，然后将它们组合以获得一个Response => Either[ThisDirection, ThatDirection]函数：

def thisResponse(response: ThisResponse): ThisDirection = ThisDirection // or any This-specific functionality

def thatResponse(response: ThatResponse): ThatDirection = ThatDirection // or any That-specific functionality

def responsePartition(response: Response): 
    Either[ThisDirection, ThatDirection] = response match {
  case r:ThisResponse => Left(thisResponse(r))
  case r:ThatResponse => Right(thatResponse(r))
}