在Scala中匹配类型

Question

是否可以在Scala中匹配类型？ 像这样：

  def apply[T] = T match {
    case String => "you gave me a String",
    case Array  => "you gave me an Array"
    case _ => "I don't know what type that is!"
  }

（但是编译，很明显:)）

也许正确的方法是类型重载……可能吗？

不幸的是，我无法将其传递给对象和模式匹配的实例。

Answer 1

def apply[T](t: T) = t match {
  case _: String => "you gave me a String"
  case _: Array[_]  => "you gave me an Array"
  case _ => "I don't know what type that is!"
}

Answer 2

您可以使用清单并对其进行模式匹配。 但是，传递数组类的情况是有问题的，因为JVM对每种数组类型使用不同的类。 要变通解决此问题，您可以检查是否有问题的类型被擦除为数组类：

val StringManifest = manifest[String]

def apply[T : Manifest] = manifest[T] match {
  case StringManifest => "you gave me a String"
  case x if x.erasure.isArray => "you gave me an Array"
  case _ => "I don't know what type that is!"
}

Answer 3

Manifest ID已弃用。 但是你可以使用TypeTag

import scala.reflect.runtime.universe._

def fn[R](r: R)(implicit tag: TypeTag[R]) {

  typeOf(tag) match {
       case t if t =:= typeOf[String] => "you gave me a String"
       case t if t =:= typeOf[Array[_]] => "you gave me an Array"
       case _ => "I don't know what type that is!"
  }
}

希望这可以帮助。