Kotlin observable properties

Properties.kt

import com.sun.jdi.InvalidTypeException
import java.util.LinkedHashSet
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

public object Properties {
	fun observable<T>(initialValue: T): ReadWriteProperty<Any?, T> {
		return ObservableProperty(initialValue)
	}
}

public fun Any.getObservers<T>(prop: KProperty<T>): Set<(T) -> Unit> {
	return getObservableProperty(prop).observers
}

public fun Any.addObserver<T>(prop: KProperty<T>, observer: (T) -> Unit) {
	getObservableProperty(prop).observers.add(observer)
}

public fun Any.addObservers<T>(prop: KProperty<T>, observers: Collection<(T) -> Unit>) {
	getObservableProperty(prop).observers.addAll(observers)
}

public fun Any.removeObserver<T>(prop: KProperty<T>, observer: (T) -> Unit) {
	getObservableProperty(prop).observers.remove(observer)
}

public fun Any.removeObservers<T>(prop: KProperty<T>, observers: Collection<(T) -> Unit>) {
	getObservableProperty(prop).observers.removeAll(observers)
}

public fun Any.retainObservers<T>(prop: KProperty<T>, observers: Collection<(T) -> Unit>) {
	getObservableProperty(prop).observers.retainAll(observers)
}

public fun Any.clearObservers<T>(prop: KProperty<T>) {
	getObservableProperty(prop).observers.clear()
}

private fun Any.getObservableProperty<T>(prop: KProperty<T>): ObservableProperty<T> {
	return try {
		getDelegate(prop) as ObservableProperty<T>
	} catch(e: ClassCastException) {
		throw InvalidTypeException("${prop.name} is of type ObservableProperty")
	} catch(e: NoSuchFieldException) {
		throw InvalidTypeException("${prop.name} is of type ObservableProperty")
	}
}

private fun Any.getDelegate<T>(prop: KProperty<T>): Any {
	return javaClass.getDeclaredField("${prop.name}\$delegate").let {
		it.setAccessible(true)
		it.get(this)
	}
}

private class ObservableProperty<T>(initialValue: T) : ReadWriteProperty<Any?, T> {
	public val observers: MutableSet<(T) -> Unit> = LinkedHashSet()
	private var value = initialValue

	public override fun get(thisRef: Any?, desc: PropertyMetadata): T {
		return value
	}

	public override fun set(thisRef: Any?, desc: PropertyMetadata, value: T) {
		this.value = value
		observers.forEach { it(value) }
	}
}