浅谈Scala模式匹配

e match {
 case Pattern1 => do Something
 case Pattern2 if-clause => do others
 ...
}

case class Player(name: String, score: Int)
def printMessage(player: Player) = player match {
 case Player(_, score) if score > 100000 =>
  println("Get a job, dude!")
 case Player(name, _) =>
  println("Hey, $name, nice to see you again!")
}

def parseArgument(arg: String) = arg match {
  //匹配值
  case "-h" | "--help" => displayHelp
  case "-v" | "--version" => displayVerion
  case whatever => unknownArgument(whatever)
}

def f(x: Any): String = x match {
  //匹配类型
  case i:Int => "integer: " + i
  case _:Double => "a double"
  case s:String => "I want to say " + s
}

case class Player(name: String, score: Int)
def message(player: Player) = player match {
 case Player(_, score) if score > 100000 =>
  "Get a job, dude!"
 case Player(name, _) =>
  "Hey, $name, nice to see you again!"
}

trait User {
 def name: String
}
class FreeUser(val name: String) extends User
object FreeUser {
 //提取器
 def unapply(user: FreeUser): Option[String] = Some(user.name)
}

 val user: User = new FreeUser("Daniel")
 user match {
  case FreeUser(name) => println("it match here" + name)
  case _ => println("not me")
 }

 val user: User = new FreeUser("Daniel")
 //将返回结果存在一个常量中
 val message = user match {
  case FreeUser(name) => "it match here" + name
  case _ => "not me"
 }
 //可以随意使用该常量，实现解耦
 println(message)