markmaynard

// Thread safe check
runBlocking {
  val deferred = (1..20).map { n ->
  GlobalScope.async {
      val r = (1..10).random()
      println("In ${n}")
      try {
        when {
          r % 2 == 0 -> {
            println("Create ${n} Thing1")

markmaynard

companion object {
  @Volatile var myThing: SomeThing? = null
    @Synchronized set(value: SomeThing?) {
      val i = myThing
      if (i != null) {
        field = i
      } else {
        field = value
      }
    }

markmaynard

sealed class SomeThing {
  abstract fun run()
  abstract fun play()
}

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

markmaynard

inline fun <reified T: SomeThing> ThingFactory(clazz: KClass<T>): ThingFactory? =
  when(clazz) {
    Thing1::class -> ThingFactory(ThingFactory.ThingType.Thing1Type)
    Thing2::class -> ThingFactory(ThingFactory.ThingType.Thing2Type)
    else -> throw RuntimeException("Unknown type: $clazz")
  }

markmaynard

interface ClassBackedEnum {
  fun toClass(): Any
}

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

markmaynard

import kotlin.reflect.KClass
import kotlinx.coroutines.*

fun main() {
  println("Welcome to Thingville, population 1")
  val factory = ThingFactory(Thing1::class)
  factory?.run() // "Run Fast!"
  factory?.play() // "Run Hard!"
  val factory2 = ThingFactory(Thing2::class) // Run Time Error: Already created as type: class Thing1
  val factory3 = ThingFactory(NoThing::class) // Compile Time Error: None of the following functions can be called with the arguments supplied: public constructor ThingFactory(clazz: ThingFactory.ThingType) defined in ThingFactory public inline fun <reified T : SomeThing> ThingFactory(clazz: KClass<???>): ThingFactory?

markmaynard

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

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

markmaynard

class ThingFactory {
    inline fun <reified T: Any> run() {
        if (myThing == null) {
        	createThing<T>()
        }
        myThing!!.run()
    }
    
    inline fun <reified T: Any> play() {
        if (myThing == null) {

markmaynard

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

markmaynard

class ThingFactory {
    inline fun <reified T: Any> run() {
        if (myThing == null) {
        	createThing<T>()
        }
        myThing!!.run()
    }
    
    inline fun <reified T: Any> play() {
        if (myThing == null) {