Scala，PartialFunction 的默认代码？

Question

我正在使用 Akka，并且想要运行一些代码用于 PartialFunction 的所有情况。对于演员监督，我有这样的东西：

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

我发现运行某些代码无需在每种情况下都重新编写的唯一方法是：

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)

我环顾四周并找到了其他答案（例如 this one），但找不到任何替代方法来替代我想出的方法。

Answer 1

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 andThen 组合任意两个函数。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
}

更一般地说：

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的问题中描述的方式。

Scala，PartialFunction 的默认代码？

Scala, default code for PartialFunction?

scala

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akka