映射失败的未来的例外

Question

什么是最干净的方式map的Exception的失败Future在Scala呢？

说我有:

import scala.concurrent._
import scala.concurrent.ExecutionContext.Implicits.global

val f = Future { 
  if(math.random < 0.5) 1 else throw new Exception("Oh no") 
}

如果未来成功1,我想保留它,但是如果它失败了我想改变Exception到另一个Exception.

我能想出的最好的是变换,但是这需要我为成功案例制定一个不必要的功能:

val f2 = f.transform(s => s, cause => new Exception("Something went wrong", cause))

有没有理由没有mapFailure(PartialFunction[Throwable,Throwable])？

Answer 1

还有:

f recover { case cause => throw new Exception("Something went wrong", cause) }

从Scala 2.12开始,您可以:

f transform {
  case s @ Success(_) => s
  case Failure(cause) => Failure(new Exception("Something went wrong", cause))
}

要么

f transform { _.transform(Success(_), cause => Failure(new Exception("Something went wrong", cause)))}

Answer 2

您可以尝试recoverWith:

f recoverWith{
  case ex:Exception => Future.failed(new Exception("foo", ex))
}