與案例類匹配的模式

每個 case 類定義一個提取器，可用於在模式匹配時捕獲 case 類的成員：

case class Student(name: String, email: String)

def matchStudent1(student: Student): String = student match {
    case Student(name, email) => s"$name has the following email: $email" // extract name and email
}

模式匹配的所有常規規則都適用 - 你可以使用保護和常量表示式來控制匹配：

def matchStudent2(student: Student): String = student match {
    case Student("Paul", _) => "Matched Paul" // Only match students named Paul, ignore email
    case Student(name, _) if name == "Paul" => "Matched Paul" // Use a guard to match students named Paul, ignore email
    case s if s.name == "Paul" => "Matched Paul" // Don't use extractor; use a guard to match students named Paul, ignore email
    case Student("Joe", email) => s"Joe has email $email" // Match students named Joe, capture their email
    case Student(name, email) if name == "Joe" => s"Joe has email $email" // use a guard to match students named Joe, capture their email
    case Student(name, email) => s"$name has email $email." // Match all students, capture name and email 
}