scala 字符串不区分大小写的模式匹配
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Case insensitive pattern matching for strings
提问by ZhekaKozlov
match (str) {
case "String1" => ???
case "String2" => ???
}
This is case sensitive matching. How to write case insensitive matching? I know I can call toLowerCase for each branch, but I want more elegant solution.
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。
回答by Andreas Neumann
Basic approach:
基本方法：
You could use Pattern Guardsand Regular Expressions
您可以使用模式保护和正则表达式
str match {
case s if s matches "(?i)String1" => 1
case s if s matches "(?i)String2" => 2
case _ => 0
}
Sophisticated method:
精妙的方法：
Implicitswith String Interpolationand Regex
Implicits与字符串插值和正则表达式
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
}
Some example usage in the REPL:
REPL 中的一些示例用法：
scala> doStringMatch("StRINg1")
res5: Int = 1
scala> doStringMatch("sTring2")
res8: Int = 2
回答by pathikrit
Another approach that does not depend on regexes or interpolaters:
另一种不依赖于正则表达式或插值器的方法：
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!")
}
Here is another way using interpolaters but no regex:
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!")
}
The above can also be used to pattern match inside case classes e.g.:
以上也可用于在 case 类中进行模式匹配，例如：
case class Dog(name: String)
val fido = Dog("FIDO")
fido match {
case Dog(ci"fido") => "woof"
case _ => "meow :("
}
回答by Antonio Maria Sanchez Berrocal
Easy solution:
简单的解决方案：
val str = "string1"
str toUpperCase match (str) {
case "STRING1" => ???
case "STRING2" => ???
}
