Case insensitive pattern matching for strings - scala

Question

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.

Answer 1

Basic approach:
You could use Pattern Guards and Regular Expressions
str match {
case s if s matches "(?i)String1" => 1
case s if s matches "(?i)String2" => 2
case _ => 0
}
Sophisticated method:
Implicits with String Interpolation and Regex
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:
scala> doStringMatch("StRINg1")
res5: Int = 1
scala> doStringMatch("sTring2")
res8: Int = 2

Answer 2

Easy solution:
val str = "string1"
str toUpperCase match (str) {
case "STRING1" => ???
case "STRING2" => ???
}

Answer 3

Another approach that does not depend on regexes or interpolaters:
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:
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.:
case class Dog(name: String)
val fido = Dog("FIDO")
fido match {
case Dog(ci"fido") => "woof"
case _ => "meow :("
}