scala - Scala，PartialFunction 的默认代码？

Question

我正在使用 Akka，并希望为 PartialFunction 的所有情况运行一些代码。对于演员监督，我有类似的东西：

val supervisorStrategy = OneForOneStrategy() {
  case npe: NullPointerException => Stop
  case re: RuntimeException => Restart
}

我发现为所有情况运行一些代码而不必在每种情况下再次编写它的唯一方法是：

val pf = new PartialFunction[Throwable, Directive] {
  def apply(throwable: Throwable) = {
    doSomething(throwable)
    throwable match {
      case NullPointerException => Stop
      case RuntimeException => Restart
    }
  }

  def isDefinedAt(throwable: Throwable) = true
}

val supervisorStrategy = OneForOneStrategy()(pf)

我环顾四周并查看了其他答案（例如这个），但找不到任何替代我想出的方法。

Answer 1

这应该这样做：

val supervisorStrategy = OneForOneStrategy() { 
 case x =>
  doSomething(x)
  x match {
    case npe: NullPointerException => Stop
    case re: RuntimeException => Restart
  }
}

Answer 2

似乎不是 Akka 特有的。您始终可以使用 组合任意两个函数andThen。具体来说：

package com.example

import akka.actor.OneForOneStrategy
import akka.actor.SupervisorStrategy.{Decider, Restart, Stop}

object Answer extends App {
  val doSomething:PartialFunction[Throwable, Throwable] = { case e =>
    println(s"doing something with $e")
    e
  }

  val decide:Decider = {
    case _:NullPointerException => Stop
    case _:RuntimeException => Restart
  }

  val strategy = OneForOneStrategy()(doSomething andThen decide)

  val errors = Seq(new NullPointerException, new RuntimeException)
  errors map strategy.decider foreach println
}

更普遍：

package com.example

object Answer extends App {
  val inspect:PartialFunction[Throwable, Throwable] = { case e =>
      println(s"inspecting $e")
      e
  }

  val decide:PartialFunction[Throwable, String] = {
    case npe:NullPointerException => "NPE!"
    case iae:IllegalArgumentException => "Bad arg!"
  }

  val combined = inspect andThen decide

  val errors = Seq(new NullPointerException, new IllegalArgumentException)
  errors map combined foreach println
}

Answer 3

感谢其他答案，但在这种 Akka 特定情况下，我无法让它们工作。例如，这不会编译：

val ft = OneForOneStrategy() { x: Throwable =>
  doSomething(x)
  x match {
    case npe: NullPointerException => Stop
    case re: RuntimeException => Stop
  }
}

Error:(48, 47) type mismatch;
found   : Throwable => akka.actor.SupervisorStrategy.Directive
required: akka.actor.SupervisorStrategy.Decider (which expands to) PartialFunction[Throwable,akka.actor.SupervisorStrategy.Directive]

我正在使用 Akka 2.4.11 和 Scala 2.11.8

对我来说唯一可行的解​​决方案是我在最初问题中描述的方式。