Generic Singleton Factory part 1 complete

gsfpt1c.kt

val factory = ThingFactory()
factory.run<Thing1>() // "Run Fast!"
factory.play<Thing1>() // "Play Hard!"
factory.play<Thing2>() // "Play Hard!" ????

interface SomeThing {
  fun run()
  fun play()
}

class Thing1: SomeThing {
  override fun run() = println("Run Fast!")
  override fun play() = println("Play Hard!")
}
class Thing2: SomeThing {
  override fun run() = println("Run Silly!")
  override fun play() = println("Play Soft!")
}

class ThingFactory {
  inline fun <reified T: Any> run() {
    if (myThing == null) {
    	createThing<T>()
    }
    myThing!!.run()
  }
    
  inline fun <reified T: Any> play() {
    if (myThing == null) {
    	createThing<T>()
    }
    myThing!!.play()
  }
    
  inline fun <reified T: Any> createThing() {
    when(T::class) {
      Thing1::class -> myThing = Thing1()
      Thing2::class -> myThing = Thing2()
      else -> throw IllegalArgumentException("Unknown thing")
    }
  }
        
  companion object {
    var myThing: SomeThing? = null
  }
}