Hi! *Is it a good idea to use `KProperty` as a ke...

# announcements

[Tianyu Zhu]

Hi!

Is it a good idea to use KProperty as a key in a Map?
• Is KProperty created compile-time? or is it created by reflection at runtime?
• Will this cause memory leaks?
For context I've defined the following:

abstract class Mixin<Value> {
  private val mixins = mutableMapOf<KProperty<*>, Value>()

  companion object Property {
    operator fun <Value, T: Value> getValue(mixin: Mixin<Value>, property: KProperty<*>): T {
      return when (val value = mixin.mixins[property]) {
        null -> throw NoSuchElementException("Uninitialized mix-in: ${property.name}")
        else -> @Suppress("UNCHECKED_CAST") (value as T)
      }
    }

    operator fun <Value> setValue(mixin: Mixin<Value>, property: KProperty<*>, value: Value) {
      mixin.mixins[property] = value
    }
  }
}

The idea is that, by extending this class, I get to make type-safe property extensions on classes that extend `Mixin`:

// A dynamically extensible class declared in some parent module
class Shipment(id: String): Mixin<Any>

// Now, let's say I want to do track shipment status in some downstream module.
var Shipment.statusHistory: List<ShipmentStatus> by Mixin // declare the mixin

// Load the status history of the shipment from the database
fun Shipment.loadStatusHistory() {
  statusHistory = statusDatabase.lookup(id)
}

// Check if the shipment is complete
val Shipment.isComplete: Boolean get() = statusHistory.any { it.state == ShipmentStatus.State.COMPLETE }