是否可以在 Scala 中对变量进行元组赋值? [英] Is it possible to have tuple assignment to variables in Scala?

问题描述

可能的重复:
元组参数声明和赋值奇怪

在 Scala 中，可以通过以下方式对元组进行多变量赋值:

In Scala, one can do multiple-variable assignment to tuples via:

val (a, b) = (1, 2)

但是类似的赋值给变量的语法似乎不起作用.例如我想这样做:

But a similar syntax for assignment to variables doesn't appear to work. For example I'd like to do this:

var (c, d) = (3, 4)
(c, d) = (5, 6)

我想在多变量赋值中重用 c 和 d.这可能吗?

I'd like to reuse c and d in multiple-variable assignment. Is this possible?

推荐答案

这不仅仅是多变量赋值"，而是全功能的模式匹配！

This isn't simply "multiple variable assignment", it's fully-featured pattern matching!

所以以下都是有效的:

val (a, b) = (1, 2)
val Array(a, b) = Array(1, 2)
val h :: t = List(1, 2)
val List(a, Some(b)) = List(1, Option(2))

这是模式匹配的工作方式，它将一些东西分解成更小的部分，并将这些部分绑定到新名称.按照规定，模式匹配不会绑定到预先存在的引用，您必须自己执行此操作.

This is the way that pattern matching works, it'll de-construct something into smaller parts, and bind those parts to new names. As specified, pattern matching won't bind to pre-existing references, you'd have to do this yourself.

var x: Int = _
var y: Int = _

val (a, b) = (1, 2)
x = a
y = b

// or

(1,2) match {
  case (a,b) => x = a; y = b
  case _ =>
}

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