Scala:在reflect.runtime.universe.Type上进行模式匹配？

Question

如何在reflect.runtime.universe.Type上进行模式匹配？

def test(t: reflect.runtime.universe.Type) {
  t match {
    case Int => \\ ...
    case Double => \\ ...
    case String => \\ ... 
    case _ =>  \\ ...
  }
}    

这不起作用,因为翻译抱怨:

error: pattern type is incompatible with expected type;
 found   : Int.type
 required: reflect.runtime.universe.Type
Note: if you intended to match against the class, try `case _: Int`
         case Int => // ...
              ^

尝试该建议也不起作用:

def test(t: reflect.runtime.universe.Type) {
  t match {
    case _: Int => \\ ...
    case _: Double => \\ ...
    case _: String => \\ ... 
    case _ =>  \\ ...
  }
}    

...

error: pattern type is incompatible with expected type;
 found   : Int
 required: reflect.runtime.universe.TypeApi
            case _: Int => // ...
                 ^

那么这个的正确语法是什么？

谢谢!

Answer 1

该TypeTagAPI有一个比较操作=:=和获取的方法Type实例给定类,你可以用后卫组合这些来获得期望的结果:

import scala.reflect.runtime.universe._

def test(t: Type) {
  t match {
    case t if t =:= typeOf[Int] => println("int")
    case t if t =:= typeOf[String] => println("string")
    case _ =>  
  }
}