递增并获得价值 [英] Incrementing and getting value

问题描述

简单的scala问题.考虑以下内容.

Simple scala question. Consider the below.

scala> var mycounter: Int = 0;
mycounter: Int = 0

scala> mycounter += 1

scala> mycounter
res1: Int = 1

在第二个语句中，我增加了我的计数器.但什么都没有返回.如何在一个语句中递增并返回某些内容.

In the second statement I increment my counter. But nothing is returned. How do I increment and return something in one statement.

推荐答案

使用 '+=' 返回单位，所以你应该这样做:

Using '+=' return Unit, so you should do:

{ mycounter += 1; mycounter }

你也可以使用闭包来实现这个技巧(因为函数参数是 val):

You can too do the trick using a closure (as function parameters are val):

scala> var x = 1
x: Int = 1

scala> def f(y: Int) = { x += y; x}
f: (y: Int)Int

scala> f(1)
res5: Int = 2

scala> f(5)
res6: Int = 7

scala> x
res7: Int = 7

顺便说一句，您可能会考虑使用不可变值，并采用这种编程风格，那么您的所有语句都会返回一些内容;)

BTW, you might consider using an immutable value instead, and embrace this programming style, then all your statements will return something ;)

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