scala 从函数返回元组
假设我有这样的东西：
def f () = {
var v = someLookupToV()
match v {
case Some(v) => (v.id, someOtherLookup(v.id))
case None => None // <<-- doesn't work, but I'm not sure what to put there!
}
}
有点假设 someLookupToV 返回一些对象，它有一个字段 id，然后我有一些基于 v.id 的其他查找。我想将这两个值作为元组返回。但是如果 Some(v) 不匹配任何内容我该怎么办？我要返回什么？无和（无，无）不起作用。 Scala 接受了 (null,null) 但我不知道这是否是正确的做法......
Lets say I have something like this:
def f () = {
var v = someLookupToV()
match v {
case Some(v) => (v.id, someOtherLookup(v.id))
case None => None // <<-- doesn't work, but I'm not sure what to put there!
}
}
Sort of assuming that someLookupToV returns some object, that has a field id, and then I have some other lookup based on v.id. I want to return both values as a tuple. But what do I do if Some(v) doesn't match anything? What do I return? None and (None,None) didnt' work. Scala accepted (null,null) but I've got no clue if that's the right thing to do...
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评论（2）
我不会让函数返回
(Int, Option[Int])，而是Option[(Int, Option[Int])]:或者更短一些：
I would not have the function return
(Int, Option[Int]), but insteadOption[(Int, Option[Int])]:or, somewhat shorter:
如果您想返回 (None, None)，您的“case Some”行需要返回 (Option, Option) 的元组。
正如示例中所写，您的
case Some正在返回 (Int, Option)。假设您的v.id是一个 Int 并且 someOtherLookup 返回一个 Option。If you want to return (None, None), your "case Some" line needs to return a tuple of (Option, Option).
As written in your example, your
case Someis returning (Int, Option). That's assuming yourv.idis an Int and someOtherLookup returns an Option.