获取密封特征的子类 [英] Getting subclasses of a sealed trait

问题描述

是否有可能(通过宏，某种形式的Shapeless automagic或其他方式)获得密封特征的子类列表:

Is it possible (via macros, some form of Shapeless automagic or otherwise) to obtain a list of the subclasses of a sealed trait:

• 在编译时?
• 在运行时?

推荐答案

您不需要任何第三方库即可完成此操作:

You don't need any 3rd party library to do this:

sealed trait MyTrait

case object SubClass1 extends MyTrait
case object SubClass2 extends MyTrait

import scala.reflect.runtime.{universe => ru}

val tpe = ru.typeOf[MyTrait]
val clazz = tpe.typeSymbol.asClass
// if you want to ensure the type is a sealed trait, 
// then you can use clazz.isSealed and clazz.isTrait
clazz.knownDirectSubclasses.foreach(println)

输出:

对象SubClass1

object SubClass1

对象SubClass2

object SubClass2

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