Question

我有一个任务，需要在Scala中连续开发N。对于板的表示，我想遍历2d数组并打印X'en O's。这是该代码：

  override def toString(): String = {
    val repres = ""

    for (rowIndex <- 0 until board.length - 1) {
      for (columnIndex <- 0 until board(rowIndex).length - 1) {
        if (board(rowIndex)(columnIndex) == Player.Player1) {
          repres + "X"
        } else if (board(rowIndex)(columnIndex) == Player.Player2) {
          repres + "O"
        } else if (board(rowIndex)(columnIndex) == Player.NoPlayer) {
          repres + "_"
        } else {
          throw new IllegalArgumentException
        }
      }
      repres + Properties.lineSeparator
    }
    repres
  }

这是木板：

var board = Array.fill[Player](rows,columns) {Player.NoPlayer}

由于某些原因，即使在调试中board.length为6，它也不会通过for循环。

我是scala的新手，所以可能有一些很明显的错误，我只是没有发现。

感谢您的帮助

Answer 1

I think the problem is not the loop. Are you expecting repres to change?

You have declared repres as an immutable String. All the operations you are doing are pretty much futile, it is creating a new String in each branch but you are not assigning it to anything. The last statement returns repres as an empty String.

Try to change the declaration to var repres.

Then each of the branches needs to change to repres = repres + "X" etc.

Note that this is not really functional. It's just Java adapted to Scala syntax.

Answer 2

您不应使用可变变量。它们使代码的可读性降低，并且难以推理，并且可能潜在地制造许多难以调试的问题。

在Scala中有95％的用例中，您不需要可变状态，因此我的建议是，您只是假装它根本不存在，直到您对语言有足够的了解以能够明确地区分其他5种语言为止％的案例。

 val repres = board.flatten.map { 
   case Player.Player1 => "X"
   case Player.Player2 => "O"
   case _ => "_"
 }.mkString
  .grouped(board.length)
  .mkString(Properties.lineSeparator)

Scala没有遍历for循环

2 个答案: