从类型中获取类型标签?

本文介绍了从类型中获取类型标签?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我可以使用 tpe 方法从 TypeTag[A] 获取 Type.但是我也可以从类型中恢复类型标签吗?

I can get a Type from a TypeTag[A] by using the tpe method. But can I also recover the type-tag from a type?

import scala.reflect.runtime.{universe => ru} import ru.{Type, TypeTag} def forward[A](implicit tt: TypeTag[A]): Type = tt.tpe def backward(t: Type): TypeTag[_] = ???

原因是我有一个使用类型标签作为映射键的 API，但在某些时候我只有类型并删除了标签.

The reason being that I have an API that uses type-tags as keys into a map, but at some point I only have the type and dropped the tag.

推荐答案

有可能:

import scala.reflect.runtime.universe._ import scala.reflect.api val mirror = runtimeMirror(getClass.getClassLoader) // whatever mirror you use to obtain the `Type` def backward[T](tpe: Type): TypeTag[T] = TypeTag(mirror, new api.TypeCreator { def apply[U <: api.Universe with Singleton](m: api.Mirror[U]) = if (m eq mirror) tpe.asInstanceOf[U # Type] else throw new IllegalArgumentException(s"Type tag defined in $mirror cannot be migrated to other mirrors.") }) assert(backward[String](forward[String]) == typeTag[String])