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入的函数

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，我尝试分别获取在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，您无法从类型A => B的函数中提取（总计）A => C或A => Either[B, C]函数。如果该函数为特定值B产生一个a1，则不会在那里定义A => C函数，反之亦然。

如果您只有A => Either[B, C]是A => Option[B]和A => Option[C]（使用_.toLeft.toOption和_.toOption，则可以做的最好。

对于您的特殊情况，您可以将ThisResponse => ThisDirection和ThatResponse => ThatDirection提取为单独的函数，然后将它们组合以获得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))
}

在Scala中分解函数

1 个答案: