派生 Scala 案例类，其成员变量与基类相同 [英] Derived Scala case class with same member variables as base

问题描述

有没有更好的方法来做到这一点?

Is there a nicer way of doing this?

scala> case class A(x : Int)
defined class A

scala> case class B(override val x : Int, y : Int) extends A(x)
defined class B

我用 B 扩展了 A 并添加了一个额外的成员变量.最好不要在 x 之前写 override val.

I'm extending A with B and adding an extra member variable. It would be nice not to have to write override val before the x.

推荐答案

我强烈建议不要从案例类继承.它对 equals 和 hashCode 有惊人的影响，在 Scala 2.8 中已被弃用.

I would strongly advise not to inherit from a case class. It has surprising effects on equals and hashCode, and has been deprecated in Scala 2.8.

相反，在特征或抽象类中定义 x.

Instead, define x in a trait or an abstract class.

scala> trait A { val x: Int }
defined trait A

scala> case class B(val x: Int, y: Int) extends A
defined class B

http://www.scala-lang.org/node/3289

http://www.scala-lang.org/node/1582

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