Scala，使用mutable var的类，在重写方法中更新 [英] Scala, class using mutable var, update in overriding method

问题描述

我很难理解如何使以下代码结构起作用。

I am having a hard time understanding how to get the following code structure to work.

在Scala中，我有一个类 MyClass ，它继承自 SomeClass 我在这种情况下添加了一个 var 成员变量，名为 mutableArray ，它正在被重写的方法<$中进行更新c $ c> overridingSomeClassMethod 并在我立即多次创建 MyClass 的新实例时调用。但是当我尝试获取更新的 mutableArray 变量时，在 main 中打印出实例化的 var 好像它是不可变的或只有覆盖方法中的范围。

In Scala I have a class MyClass which inherits from SomeClass I added a var member variable in this case called mutableArray and it is being updated in the overridden method overridingSomeClassMethod and is called when I create a new instance of the MyClass a number of times right away. But in main when I try and get the updated mutableArray variable it prints out the instantiated var as if it is immutable or only has scope in the overriding method.

我无法更改父 SomeClass ，我尝试创建一个伴随对象，并将变量放在包含 SomeOtherObject 中，但我得到了同样的问题。

I can't change the method in parent SomeClass, and I tried creating a companion object as well as putting the variable in the encompassing SomeOtherObject but I get the same exact issue.

import scala.collection.mutable.ArrayBuffer

object SomeOtherObject{
  case MyClass(...) extends SomeClass(..){
    var mutableArray: ArrayBuffer[Int] = ArrayBuffer.fill(5)(0)

    def overridingSomeClassMethod(...){
      var someReturnVar = 0.0
      mutableArray(0) += 1
      println(mutableArray.mkString) // last output -> 84169
      someReturnVar
    }
  }

  def main(args: Array[String]){
    var mc = new MyClass
    println(mc.mutableArray.mkString) // output -> 00000
  }
}

推荐答案

您可以使用早期初始化程序：

case MyClass(...) extends {
  var mutableArray: ArrayBuffer[Int] = ArrayBuffer.fill(5)(0)
} with SomeClass(..) {

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