scala's尝试优雅的错误行为

Question

在scala中有更优雅的方法吗？

def doTheDangerousThing(): Try[Result] = {
  val result = Try(dangerousOp)

  if (result.isFailure) {
     println("error")
  }

  result
}

Answer 1

我认为你的if语句完全有效。 这是另一种选择：

def doTheDangerousThing(): Try[Result] = Try(dangerousOp) recoverWith {
    case exception => println("error"); Failure(exception)
}

Answer 2

像这样的东西：

   def doTheDangerousThing[Result](dangerousOp: =>Result): Try[Result] = Try(dangerousOp) match {
    case o @ Failure(_) =>  println("error"); o
    case _ => _
  }

Answer 3

不确定这是否更为惯用，但有时我发现以这种方式放置recoverWith可以提高我的可读性：

def doDangerousThing(): Try[Result] = Try {
  dangerousOp
} recoverWith {
  case t: Throwable => println("error"); Failure(t)
}

Answer 4

我的首选，

def doTheDangerousThing(): Option[Result] = Try (dangerousOp) toOption

如果Try成功，您将获得Some(value) ，如果它失败则为None 。

有关Try uses的大型编译， Try 参阅Scala 2.10.0中的Try介绍 。

Answer 5

有方法。 例如：

def doTheDangerousThing(): Try[Result] = {
  val result = Try(dangerousOp)

  result.failed foreach { _ =>
     println("error")
  }

  result
}

或者，如果您不想重复result ，那么：

def doTheDangerousThing(): Try[Result] = {
  Try(dangerousOp) recover {
    case ex => println("error"); throw ex
  }
}

Answer 6

在某些情况下，我喜欢使用两步法，这将允许我更细粒度的错误消息控制：

  def retrieveData(dataId: String): Try[String] = {
    Try {
      Option(someApi(dataId))
        .getOrElse(throw SomeApiFailedException("invalid dataId"))
    } recoverWith {
      case e: SomeApiFailedException => Failure(e)
      case e: Throwable => Failure(SomeApiFailedException("failed retrieve dataId"))
    }
  }

  case class SomeApiFailedException(err: String) extends RuntimeException(err)

Answer 7

好吧，我想你可以这样做：

def doTheDangerousThing(): Option[Result] = 
  Try(dangerousOp) match {
    case Success(result) => Some(result)
    case Failure(e) => None //might want to log the error as well
  }

Answer 8

我可以从三种实现中的任何一种中进行选择，具体取决于我是否要：

• 只需将其向上传播（ doTheDangerousThing1 ）
• 忽略错误（ doTheDangerousThing2 ）
• 向上传播时拦截错误（ doTheDangerousThing3 ）

这是代码：

import scala.util.{Try,Success,Failure}
object temp {
  type Result = Int

  def dangerousOp = {
    val r = scala.util.Random.nextInt(10)
    if (r > 5) r else throw new RuntimeException("Failed on " + r)
  }
  def logMessage[T](t: T) = println(t)

  def doTheDangerousThing1(): Try[Result] = Try(dangerousOp)

  def doTheDangerousThing2(): Option[Result] = {
    Try(dangerousOp) match {
      case Success(r) => Option(r)
      case _ => None
    }
  }


  def doTheDangerousThing3(): Try[Result] = {
    Try(dangerousOp) match {
      case t @ Success(r) => t
      case t @ _ => logMessage("failed: "+t); t
    }
  }
}

在REPL里面

scala> doTheDangerousThing1
res0: scala.util.Try[Result] = Success(9)

scala> doTheDangerousThing1
res1: scala.util.Try[Result] = Success(9)

scala> doTheDangerousThing2
res2: Option[Result] = None

scala> doTheDangerousThing2
res3: Option[Result] = Some(7)

scala> doTheDangerousThing3
failed: Failure(java.lang.RuntimeException: Failed on 0)
res4: scala.util.Try[Result] = Failure(java.lang.RuntimeException: Failed on 0)

scala> doTheDangerousThing3
failed: Failure(java.lang.RuntimeException: Failed on 0)
res5: scala.util.Try[Result] = Failure(java.lang.RuntimeException: Failed on 0)