scala - 传递状态而不用隐式混淆代码

Question

我有一个看起来像这样的层次结构：

trait Player
trait Player1 extends Player
trait Player2 extends Player
trait Human extends Player
trait Computer extends Player

我有一个函数文字，它将用户输入映射到 Players 类型的实例，其中type Players = Tuple2[Player1, Player2]：

val initialize: Array[String] => Players = (args: Array[String]) =>
  args.map(_.trim.toLowerCase) match {
    case Array("x") =>
      (new Player1 with Human, new Player2 with Computer)
    case Array("o") =>
      (new Player1 with Computer, new Player2 with Human)
    case _ =>
      (new Player1 with Human, new Player2 with Computer)
    }

有没有一种方法可以让我的其他班级知道，Players而不必到处隐式传递 Players？例如

def nextPlayer(player: Player)(implicit players: Players): Player =
  player match {
    case _: Player1 => players._2
    case _: Player2 => players._1
  }

我想尽可能地避免副作用，所以我没有使用过类似的东西：

object GameState {
  var player1: Player = _
  var player2: Player = _
}

然而，这将是绕过必须传递Players给所有需要它的方法的唯一方法吗？

Answer 1

将单个玩家嵌入到一个Players类中：

class Players(init: Array[String]) { players =>  
  trait Player
  ...
  val (p1, p2) = init.map(_.trim.toLowerCase match {
    case Array("x") => (new Player1 with Human, new Player2 with Human)
    ...
  }

  def nextPlayer(player: Player): Player = if (player eq p1) p2 else p1
  ...
}