Returns a property delegate for a read/write property with a non-null value that is initialized not during object construction time but at a later time. Trying to read the property before the initial value has been assigned results in an exception.

fun <T : Any> notNull(): ReadWriteProperty<Any?, T>

Returns a property delegate for a read/write property that calls a specified callback function when changed.

fun <T> observable(
    initialValue: T, 
    onChange: (property: KProperty<*>, oldValue: T, newValue: T) -> Unit
): ReadWriteProperty<Any?, T>

Returns a property delegate for a read/write property that calls a specified callback function when changed, allowing the callback to veto the modification.

fun <T> vetoable(
    initialValue: T, 
    onChange: (property: KProperty<*>, oldValue: T, newValue: T) -> Boolean
): ReadWriteProperty<Any?, T>