Weak reference property delegate in Kotlin

WeakReferenceProperty.kt

class WeakReferenceProperty<T>(private val creator: () -> T) {

    private var value: WeakReference<T> =
            WeakReference(creator())

    operator fun getValue(thisRef: Any?, property: KProperty<*>): T =
            value.get() ?: creator().also { value = WeakReference(it) }
}

private fun <T> weak(creator: () -> T) =
        WeakReferenceProperty(creator)

You may write simple like this:

class WeakRefHolder<T>(private var value: WeakReference<T?>) {

    operator fun getValue(thisRef: Any?, property: KProperty<*>): T? {
        return value.get()
    }

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T?) {
        this.value = WeakReference(value)
    }
}

fun <T> weak(value: T) = WeakRefHolder(WeakReference(value))