A Dependency Injection Framework that fits in a toot: https://androiddev.social/@py/111769799220786590

CoffeeParts.kt

class CoffeeLogger {
  fun log(msg: String) {
    println(msg)
  }
}

interface Heater {
  fun on()
  fun off()
  val isHot: Boolean
}

class ElectricHeater(private val logger: CoffeeLogger) : Heater {
  override var isHot = false
    private set

  override fun on() {
    isHot = true
    logger.log("~ ~ ~ heating ~ ~ ~")
  }

  override fun off() {
    isHot = false
  }
}

interface Pump {
  fun pump()
}

class Thermosiphon(
  private val logger: CoffeeLogger,
  private val heater: Heater
) : Pump {
  override fun pump() {
    if (heater.isHot) {
      logger.log("=> => pumping => =>")
    }
  }
}

class CoffeeMaker(
  private val logger: CoffeeLogger,
  private val heater: Heater,
  private val pump: Pump
) {

  fun brew() {
    heater.on()
    pump.pump()
    logger.log(" [_]P coffee! [_]P ")
    heater.off()
  }
}

Linker.kt

class Linker {
  val factories = mutableMapOf<Class<out Any?>, Linker.() -> Any?>()
}

inline fun <reified T> Linker.install(noinline factory: Linker.() -> T) {
  factories[T::class.java] = factory
}

inline fun <reified T> Linker.get(): T {
  return factories.getValue(T::class.java)() as T
}

inline fun <reified T> Linker.installSingleton(noinline factory: Linker.() -> T) {
  var instance = UNINITIALIZED
  install {
    if (instance === UNINITIALIZED) {
      instance = factory()
    }
    instance as T
  }
}

var UNINITIALIZED: Any? = Any()

Main.kt

fun main() {
  val logModule = Linker()
  logModule.installSingleton {
    CoffeeLogger()
  }

  val partsModule = Linker()
  partsModule.installSingleton<Heater> {
    ElectricHeater(get())
  }
  partsModule.install<Pump> {
    Thermosiphon(get(), get())
  }

  val appModule = Linker()
  appModule.install {
    CoffeeMaker(get(), get(), get())
  }

  appModule.factories += logModule.factories + partsModule.factories

  val maker = appModule.get<CoffeeMaker>()
  maker.brew()
}