Enum for class instantiation

enumfactory.kt

interface ClassBackedEnum {
  fun toClass(): Any
}

class ThingFactory private constructor() {
  enum class ThingType(): ClassBackedEnum {
    Thing1Type {
      override fun toClass() = Thing1::class
    },
    Thing2Type {
      override fun toClass() = Thing2::class
    }
  }

  constructor (clazz: ThingType): this() {
    if (myThing == null) {
      when(clazz.toClass()) {
        Thing1::class -> myThing = Thing1()
        Thing2::class -> myThing = Thing2()
      }
    } else {
      if (myThing?.javaClass?.kotlin != clazz.toClass()) {
        throw RuntimeException("Already created as type:${myThing?.javaClass?.kotlin}")
      }
    }
  }
    
  fun run() {
    myThing?.run()?: throw RuntimeException("Singleton not instantiated")
  }

  fun play() {
    myThing?.play()?: throw RuntimeException("Singleton not instantiated")
  }
}