如何在 Scala 中执行类似的操作?
case class Foo[A](x: A) {
def get[T]: Option[T] = x match {
case x: T => Some(x) // if x is of type T i.e. T =:= A
case _ => None
}
}
val test = Foo("hi")
assert(test.get[Int] == None)
assert(test.get[String] == Some("hi"))
我尝试了这个,但遇到了一些奇怪的时间推断失败:
import scala.util.{Try, Success}
import reflect._
case class Foo[A](x: A) extends Dynamic {
def get[T: ClassTag]: Option[T] = Try(x.asInstanceOf[T]) match {
case Success(r) => Some(r)
case _ => None
}
}
object Foo extends App {
val test = Foo("hi")
val wtf: Option[Int] = test.get[Int]
assert(wtf.isInstanceOf[Option[String]])
assert(wtf == Some("hi")) // how????
// val wtf2: Option[String] = wtf // does not compile even if above assert passes!!
}
最佳答案
肯定是个骗子,但仓促:
scala> :pa
// Entering paste mode (ctrl-D to finish)
import reflect._
case class Foo[A](x: A) {
def get[T: ClassTag]: Option[T] = x match {
case x: T => Some(x) // if x is of type T i.e. T =:= A
case _ => None
}
}
// Exiting paste mode, now interpreting.
import reflect._
defined class Foo
scala> val test = Foo("hi")
test: Foo[String] = Foo(hi)
scala> test.get[Int]
res0: Option[Int] = None
scala> test.get[String]
res1: Option[String] = Some(hi)
关于Scala 检查泛型类型,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22341339/