Scala abstract class function call

Question

I am new to scala and I apologize in advance if the question is stupid. I am browsing through this scala code and I am confused how the following code works

abstract class ClusterSimulatorDesc(val runTime: Double) {
  def newSimulator(constantThinkTim: Double,
               perTaskThinkTime: Double,
               blackListPercent: Double,
               schedulerWorkloadsToSweepOver: Map[String, Seq[String]],
               workloadToSchedulerMap: Map[String, Seq[String]],
               cellStateDesc: CellStateDesc,
               workloads: Seq[Workload],
               prefillWorkloads: Seq[Workload],
               logging: Boolean = false): ClusterSimulator
}

class ClusterSimulator(val cellState: CellState,
                   val schedulers: Map[String, Scheduler],
                   val workloadToSchedulerMap: Map[String, Seq[String]],
                   val workloads: Seq[Workload],
                   prefillWorkloads: Seq[Workload],
                   logging: Boolean = false,
                   monitorUtilization: Boolean = true,
                   monitoringPeriod: Double = 1.0)
                  extends Simulator(logging) {

Now if i have a function call like:-

simulatorDesc: ClusterSimulatorDesc
val simulator =
              simulatorDesc.newSimulator(constantThinkTime,
                                         perTaskThinkTime,
                                         blackListPercent,
                                         schedulerWorkloadsToSweepOver,
                                         schedulerWorkloadMap,
                                         workloadDesc.cellStateDesc,
                                         workloads,
                                         prefillWorkloads,
                                         logging)

Now the question I have is, what does "ClusterSimulator" at the end of the abstract class declaration does? And, how does the calling of "newSimulator" function happen, considering that its declared in an abstract class?

You can read up on Inheritance (OOP concept). Here is a brief info: scala-lang.org/old/node/125. More detailed: artima.com/pins1ed/composition-and-inheritance.html — yǝsʞǝla
– yǝsʞǝla, Commented Jul 12, 2016 at 1:32

jwvh · Accepted Answer · 2016-07-12 01:33:31Z

2

def newSimulator(....): ClusterSimulator

The method newSimulator(), when invoked, returns an instance of ClusterSimulator.

simulatorDesc: ClusterSimulatorDesc

ClusterSimulatorDesc can't be instantiated because it is abstract, but a class that extends ClusterSimulatorDesc can be instantiated and an instance of that class is also an instance of ClusterSimulatorDesc and can invoke its methods.

answered Jul 12, 2016 at 1:33

jwvh

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