Kotlin Standard Library Cookbook

How to do it...

1. Define the custom property delegate called ObservableVetoableDelegate as a subclass of the ObservableProperty class:

class ObservableVetoable<T>(initialValue: T,                          val updatePrecondition: (old: T, new: T)                           -> Boolean,                          val updateListener: (old: T, new: T)                           -> Unit) :        ObservableProperty<T>(initialValue = initialValue) {    override fun beforeChange(property: KProperty<*>,                              oldValue: T,                              newValue: T): Boolean =            updatePrecondition(oldValue, newValue)    override fun afterChange(property: KProperty<*>,                             oldValue: T,                             newValue: T) =             updateListener(oldValue, newValue)}

2. Define the initialTemperature, updatePrecondition, and updateListener arguments required by the ObservableVetoable class:

val initialTemperature = 1val updatePrecondition: ...