Question

所以这是我的代码：

val regexMeter = """^\s*(\d+,*\d+)\s*[m]\s*$""".r
val regexCentimeter = """^\s*(\d+,*\d+)\s*cm\s*$""".r
val regexDecimeter = """^\s*(\d+,*\d+)\s*dm\s*$""".r
val regexMillimeter = """^\s*(\d+,*\d+)\s*mm\s*$""".r

val height = scala.io.StdIn.readLine("Please insert the height of your shape:")
height match {
  case regexMeter(value) => val newValue = value.toDouble*100
  case regexCentimeter(value) => val newValue = value.toDouble
  case regexDecimeter(value) => val newValue = value.toDouble*10
  case regexMillimeter(value) => val newValue = value.toDouble/10
  case _ => throw new IllegalArgumentException
}

所以我的输入是例如：＆＃34; 21m＆＃34;并且它只获取21并且如果它的正则表达式与米匹配，它将它分配给val newValue并用它做一些事情。但是，当我现在想要打印那个值newValue时，它说它无法找到价值？如何从这个匹配案例中返回此val？

Answer 1

在Scala中，几乎所有东西都是表达式并返回一个值，包括模式匹配：

val newValue = height match {
    case regexMeter(value) => value.toDouble*100
    case regexCentimeter(value) => value.toDouble
    case regexDecimeter(value) => value.toDouble*10
    case regexMillimeter(value) => value.toDouble/10
    case _ => throw new IllegalArgumentException
}

Scala从匹配大小写

1 个答案: