合并多个案例时如何引用变量？

Question

当使用matchin 组合多个案例时，是否可以给变量赋予引用名称Scala？

码：

假设Gender枚举有一个像三个可能的值male，female和other。

(nameOption, genderOption) match {
    case (Some(name), Some(Gender.Male)) | (Some(name), Some(Gender.FeMale))=> s"$name gender is either male or female"
    case (None, Some(Gender.Male)) | (None, Some(Gender.FeMale)) => //some print statement
    case (Some(name), Some(Gender.Other)) =>  //some print statement
    case _ => //some print statement
}

第一种情况case (Some(name), Some(Gender.Male)) | (Some(name), Some(Gender.FeMale))是name在范围中已经定义的编译器错误。

如果在我的实际代码中不合并案例，则循环复杂性会增加。

Answer 1

您可以将第一种情况替换为：

case (Some(name), Some(Gender.Male) |  Some(Gender.FeMale))=> s"$name gender is either male or female"

更新-更好-感谢@Astrid

case (Some(name), Some(Gender.Male | Gender.FeMale)) => s"$name gender is either male or female"

Answer 2

您可以尝试以下

(nameOption, genderOption) match {
    case (Some(name), Some(gender) if (gender == Gender.Male || gender == Gender.Female) => s"$name gender is either male or female"

}

Answer 3

除了已经给出的答案之外，如果您发现自己Gender.Male | Gender.FeMale在代码的不同部分重复了match子句，则可能需要考虑使用自定义提取器。

object BinaryGender {
  def unapply(gender: Gender.Gender) : Option[Gender.Gender] = {
    Some(gender).filter(_ != Gender.Other)
  }
}

(nameOption, genderOption) match {
  case (Some(name), Some(BinaryGender(_))) => s"$name gender is either male or female"
  case (None, Some(BinaryGender(_))) => //some print statement
  ...
}