Scala stream and ExecutionContext issue - scala

Question

I'm new in Scala and i'm facing a few problems in my assignment :
I want to build a stream class that can do 3 main tasks : filter,map,and forEach.
My streams data is an array of elements. Each of the 3 main tasks should run in 2 different threads on my streams array.
In addition, I need to divde the logic of the action and its actual run to two different parts. First declare all tasks in stream and only when I run stream.run() I want the actual actions to happen.
My code :
class LearningStream[A]() {
val es: ExecutorService = Executors.newFixedThreadPool(2)
val ec = ExecutionContext.fromExecutorService(es)
var streamValues: ArrayBuffer[A] = ArrayBuffer[A]()
var r: Runnable = () => "";
def setValues(streamv: ArrayBuffer[A]) = {
streamValues = streamv;
}
def filter(p: A => Boolean): LearningStream[A] = {
var ls_filtered: LearningStream[A] = new LearningStream[A]()
r = () => {
println("running real filter..")
val (l,r) = streamValues.splitAt(streamValues.length/2)
val a:ArrayBuffer[A]=es.submit(()=>l.filter(p)).get()
val b:ArrayBuffer[A]=es.submit(()=>r.filter(p)).get()
ms_filtered.setValues(a++b)
}
return ls_filtered
}
def map[B](f: A => B): LearningStream[B] = {
var ls_map: LearningStream[B] = new LearningStream[B]()
r = () => {
println("running real map..")
val (l,r) = streamValues.splitAt(streamValues.length/2)
val a:ArrayBuffer[B]=es.submit(()=>l.map(f)).get()
val b:ArrayBuffer[B]=es.submit(()=>r.map(f)).get()
ls_map.setValues(a++b)
}
return ls_map
}
def forEach(c: A => Unit): Unit = {
r=()=>{
println("running real forEach")
streamValues.foreach(c)}
}
def insert(a: A): Unit = {
streamValues += a
}
def start(): Unit = {
ec.submit(r)
}
def shutdown(): Unit = {
ec.shutdown()
}
}
my main :
def main(args: Array[String]): Unit = {
var factorial=0
val s = new LearningStream[String]
s.filter(str=>str.startsWith("-")).map(s=>s.toInt*(-1)).forEach(i=>factorial=factorial*i)
for(i <- -5 to 5){
s.insert(i.toString)
}
println(s.streamValues)
s.start()
println(factorial)
}
The main prints only the filter`s output and the factorial isnt changed (still 1).
What am I missing here ?

Answer 1

My solution: #Levi Ramsey left a few good hints in the comments if you want to get hints and not the real solution.
First problem: Only one command (filter) run and the other didn't. solution: insert to the runnable of each command a call for the next stream via:
ec.submit(ms_map.r)
In order to be able to close all sessions, we need to add another LearningStream data member to the class. However we can't add just a regular LearningStream object because it depends on parameter [A]. Therefore, I implemented a trait that has the close function and my data member was of that trait type.