如何在 Scala 中组合选项值? [英] How to combine Option values in Scala?

问题描述

我希望能够应用一个操作 f: (T,T) =>Scala 中的 T 到 Option[T] 值.如果两个值中的任何一个为 None，我希望结果为 None.

I want to be able to apply an operation f: (T,T) => T to Option[T] values in Scala. I want the result to be None if any of the two values is None.

更具体地说，我想知道是否有更短的方法来执行以下操作:

More specifically, I want to know if there is a shorter way to do the following:

def opt_apply[T](f: (T,T) => T, x: Option[T], y: Option[T]): Option[T] = {
  (x,y) match {
    case (Some(u),Some(v)) => Some(f(u,v))
    case _ => None
  }
}

我试过 (x zip y) map {case (u,v) =>f(u,v)} 但结果是 Iterator[T] 而不是 Option[T].

I have tryied (x zip y) map {case (u,v) => f(u,v)} but the result is an Iterator[T] not an Option[T].

推荐答案

scala> val (x, y) = (Some(4), Some(9))
x: Some[Int] = Some(4)
y: Some[Int] = Some(9)

scala> def f(x: Int, y: Int) = Math.max(x, y)
f: (x: Int,y: Int)Int

scala> for { x0 <- x; y0 <- y } yield f(x0, y0)
res26: Option[Int] = Some(9)

scala> val x = None
x: None.type = None

scala> for { x0 <- x; y0 <- y } yield f(x0, y0)
res27: Option[Int] = None

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