在 Scala 中尝试，反之亦然 [英] Either to Try and vice versa in Scala

问题描述

在 Scala 标准库中是否有任何从 Either 到 Try 的转换，反之亦然?也许我遗漏了一些东西，但我没有找到.

Are there any conversions from Either to Try and vice versa in the Scala standard library ? Maybe I am missing something but I did not find them.

推荐答案

据我所知，这在标准库中是不存在的.尽管 Either 通常与 Left 失败而Right 成功一起使用，但它确实旨在支持两个概念可能的返回类型，其中一个不一定是失败案例.我猜这些人们期望存在的转换并不存在，因为 Either 并没有像 Try 那样真正设计为成功/失败 monad.话虽如此，自己丰富 Either 并添加这些转换将非常容易.这可能看起来像这样:

To the best of my knowledge this does not exist in the standard library. Although an Either is typically used with the Left being a failure and the Right being a success, it was really designed to support the concept of two possible return types with one not necessarily being a failure case. I'm guessing these conversions that one would expect to exist do not exist because Either was not really designed to be a Success/Fail monad like Try is. Having said that it would be pretty easy to enrich Either yourself and add these conversions. That could look something like this:

object MyExtensions {
  implicit class RichEither[L <: Throwable,R](e:Either[L,R]){
    def toTry:Try[R] = e.fold(Failure(_), Success(_))
  }

  implicit class RichTry[T](t:Try[T]){
    def toEither:Either[Throwable,T] = t.transform(s => Success(Right(s)), f => Success(Left(f))).get
  }  
}

object ExtensionsExample extends App{
  import MyExtensions._

  val t:Try[String] = Success("foo")
  println(t.toEither)
  val t2:Try[String] = Failure(new RuntimeException("bar"))
  println(t2.toEither)

  val e:Either[Throwable,String] = Right("foo")
  println(e.toTry)
  val e2:Either[Throwable,String] = Left(new RuntimeException("bar"))
  println(e2.toTry)
}

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