字符串的不区分大小写的模式匹配

Question

match (str) {
  case "String1" => ???
  case "String2" => ???
}

这是区分大小写的匹配.如何编写不区分大小写的匹配？我知道我可以为每个分支调用toLowerCase,但我想要更优雅的解决方案.

Answer 1

基本方法:

您可以使用Pattern Guards和Regular Expressions

str match {
case s if s matches "(?i)String1" => 1
case s if s matches "(?i)String2" => 2
case _ => 0
}

复杂的方法:

使用字符串插值和正则表达式进行隐含

implicit class CaseInsensitiveRegex(sc: StringContext) {
  def ci = ( "(?i)" + sc.parts.mkString ).r
}

def doStringMatch(str: String) = str match {
  case ci"String1" => 1
  case ci"String2" => 2
  case _ => 0
}

REPL中的一些示例用法:

scala> doStringMatch("StRINg1")
res5: Int = 1

scala> doStringMatch("sTring2")
res8: Int = 2

Answer 2

另一种不依赖于正则表达式或插值符的方法:

 implicit class StringExtensions(val s: String) extends AnyVal {
    def insensitive = new {
      def unapply(other: String) = s.equalsIgnoreCase(other)
    }
  }

  val test1 = "Bye".insensitive
  val test2 = "HELLo".insensitive

  "Hello" match {
    case test1() => println("bad!")
    case test2() => println("sweet!")
    case _ => println("fail!")
  }

这是使用插值器但没有正则表达式的另一种方法:

  implicit class StringInterpolations(sc: StringContext) {
    def ci = new {
      def unapply(other: String) = sc.parts.mkString.equalsIgnoreCase(other)
    }
  }

  "Hello" match {
    case ci"Bye" => println("bad!")
    case ci"HELLO" => println("sweet!")
    case _ => println("fail!")
  }

以上内容也可用于模式匹配案例类,例如:

case class Dog(name: String)

val fido = Dog("FIDO")

fido match {
  case Dog(ci"fido") => "woof"    
  case _ => "meow :("    
}

Answer 3

简单的解决方案：

val str = "string1"

str toUpperCase match (str) {
  case "STRING1" => ???
  case "STRING2" => ???
}