在 Scala 中，如何重新分配元组值? [英] In Scala, how can I reassign tuple values?

问题描述

我正在尝试执行以下操作

I'm trying to do something like the following

var tuple = (1, "test")
tuple._2 = "new"

但是这不会编译它抱怨 val

However this does not compile it complains about val

推荐答案

您不能重新分配元组值.它们是故意不可变的:一旦你创建了一个元组，你就可以确信它永远不会改变.这对于编写正确的代码非常有用！

You can't reassign tuple values. They're intentionally immutable: once you have created a tuple, you can be confident that it will never change. This is very useful for writing correct code!

但是如果你想要一个不同的元组怎么办?这就是复制方法的用武之地:

But what if you want a different tuple? That's where the copy method comes in:

val tuple = (1, "test")
val another = tuple.copy(_2 = "new")

或者如果您真的想使用 var 来包含元组:

or if you really want to use a var to contain the tuple:

var tuple = (1, "test")
tuple = tuple.copy(_2 = "new")

或者，如果您真的、真的希望单独更改您的值，您可以改用 case 类(可能带有隐式转换，以便您可以在需要时获得元组):

Alternatively, if you really, really want your values to change individually, you can use a case class instead (probably with an implicit conversion so you can get a tuple when you need it):

case class Doublet[A,B](var _1: A, var _2: B) {}
implicit def doublet_to_tuple[A,B](db: Doublet[A,B]) = (db._1, db._2)
val doublet = Doublet(1, "test")
doublet._2 = "new"

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