How to do thread intercommunication with shared object in Scala? - scala

Question

In the below code, first of all we can create the something with calling create method, and for destroying it we can call destroy method, each method at first changes the status of the object, then asynchronously wait until the time of the operation is up. assume that time of creating is 10 seconds and time for destroying is 5 second. when I call destroy method, it changes the destroying boolean to true, then another threads that is waiting for the creation duration will break the loop in the waitUntil method. but it does not work properly. when I call create method, it changes the status and then creates a thread to wait until the time of the creation duration goes up. after calling create method, I call destroy method as below:
map(0, 0).create(....)
map(0, 0).destroy(....)
But changing the destroying variable in destroy method did not act the another thread that is in the creating block to break and it continue until the end of duration.
#volatile
protected var status: UnitStatus = UnitStatus.NEED_TO_CREATE
#volatile
protected var destroying = false
def destroy(f: Int => Unit): Unit = status match {
case UnitStatus.DESTROYED => {
throw new UnitAlreadyDestroyedException
}
case UnitStatus.DESTROYING =>
case UnitStatus.PREPARED_TO_DESTROY => {
destroying = true
status = UnitStatus.DESTROYING
async {
waitUntil(destroyDuration, UnitStatus.DESTROYED) {
f
}
}
}
}
def create(f: Int => Unit): Unit = status match {
case UnitStatus.DESTROYED => throw new UnitAlreadyDestroyedException
case UnitStatus.NEED_TO_CREATE => {
ResourcesContainer -= creationCost
status = UnitStatus.CONSTRUCTION
async {
waitUntil(creationDuration, UnitStatus.READY) {
f
}
}
}
case _ => throw new UnitAlreadyCreatedException
}
def waitUntil(seconds: Int, finalState: UnitStatus)(f: Int => Unit): Unit = {
var timeElapse = 0
var percent: Int = 0
breakable {
while (timeElapse < seconds) {
val destroyState = isInDestroyState
if (destroying && !destroyState) {
break() // **program does not enter to this part of code**
}
timeElapse += 1
percent = ((timeElapse.asInstanceOf[Float] / seconds) * 100).toInt
f(percent)
Thread.sleep(1000)
}
if (status != null) {
status = finalState
}
}
}
def async[T](fn: => Unit): Unit = scala.actors.Actor.actor {
fn
}
def isInDestroyState: Boolean = {
status == UnitStatus.DESTROYED ||
status == UnitStatus.DESTROYING ||
status == UnitStatus.PREPARED_TO_DESTROY
}