如何增加在Scala中传递给函数的整数变量? [英] how do I increment an integer variable I passed into a function in Scala?

问题描述

我在函数外部声明了一个变量，如下所示:

I declared a variable outside the function like this:

var s: Int = 0

通过了这样的请求:

def function(s: Int): Boolean={

   s += 1

   return true

}

但是对于我来说，错误行不会消失在"s + ="下.我尝试了一切.我是Scala btw的新手.

but the error lines wont go away under the "s +=" for the life of me. I tried everything. I am new to Scala btw.

推荐答案

首先，我要重申我的警告:以下解决方案既晦涩又效率低，如果可能的话，请坚持下去和val ues.

First of all, I will repeat my words of caution: solution below is both obscure and inefficient, if it possible try to stick with values.

implicit class MutableInt(var value: Int) {
  def inc() = { value+=1 } 
}

def function(s: MutableInt): Boolean={
   s.inc() // parentheses here to denote that method has side effects
   return true
}

这是运行中的代码:

scala> val x: MutableInt = 0 
x: MutableInt = MutableInt@44e70ff

scala> function(x)
res0: Boolean = true

scala> x.value
res1: Int = 1

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