Scala Trait 如何覆盖派生的 toString Case Class

Question

我的背景是 C++/C，我正在尝试学习 scala。我很难理解特征的 toString 方法如何覆盖从特征派生的 case class 。默认情况 class 的 toString 方法当然应该覆盖特征的方法吗？我遗漏了一些明显的东西？

代码

trait Computer {
  def ram: String
  def hdd: String
  def cpu: String

  override def toString = "RAM= " + ram + ", HDD=" + hdd + ", CPU=" + cpu

}

private case class PC(ram: String, hdd: String, cpu: String) extends Computer 

private case class Server(ram: String, hdd: String, cpu: String) extends Computer

object ComputerFactory {
  def apply(compType: String, ram: String, hdd: String, cpu: String) = compType.toUpperCase match {
    case "PC" => PC(ram, hdd, cpu)
    case "SERVER" => Server(ram, hdd, cpu)
  }
}
val pc = ComputerFactory("pc", "2 GB", "500 GB", "2.4 GHz");
val server = ComputerFactory("server", "16 GB", "1 TB", "2.9 GHz");

println("Factory PC Config::" + pc);
println("Factory Server Config::" + server);

Answer 1

SLS这一点很清楚

Every case class implicitly overrides some method definitions of class scala.AnyRef unless a definition of the same method is already given in the case class itself or a concrete definition of the same method is given in some base class of the case class different from AnyRef. In particular:

Method toString: String returns a string representation which contains the name of the class and its elements.

因为 trait Computer 提供了 toString 的具体定义，并且是 PC 和 Server 的基础 class，所以 Computer.toString 是用过。

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