Pass values between 2 methods of same Object in Scala - scala

Question

I wish to pass the value of var/val from one method to another.
eg, I have
object abc {
def onStart = {
val startTime = new java.sql.Timestamp( new Date())
}
def onEnd = {
//use startTime here
}
}
calling:
onStart()
executeReports(reportName, sqlContexts)
onEnd()
Here onStart() and onEnd() are job monitoring functions for executeReports().
executeReports() runs in a loop for 5 reports.
I have tried using global variables like
object abc{
var startTime : java.sql.Timestamp = _
def onStart = {
startTime = new java.sql.Timestamp( new Date())
}
def onEnd = {
//use startTime here
}
}
but the catch with this is when the loop executes for the next report, the startTime does not change.
I also tried using Singleton Class that did not work for me either.
My requirement is to have a startTime for every iteration i.e, for every report.
Any ideas are welcome here. I'll be happy to provide more clarification on my requirement if needed.

Answer 1

The common Scala solution to this is to write a function that wraps other functions and performs the setup and shutdown internally.
def timeit[T]( fun: => T ): T = {
val start = System.currentTimeMillis //Do your start stuff
val res = fun
println (s"Time ${System.currentTimeMillis - start}") // Do your end stuff
res
}

Answer 2

RussS has the better solution, but if for some reason you're wedded to the design you've described, you might try using a mutable val, i.e. a mutable collection.
I got this to compile and pass some small tests.
object abc {
private val q = collection.mutable.Queue[java.sql.Timestamp]()
def onStart = {
q.enqueue(new java.sql.Timestamp(java.util.Calendar.getInstance().getTime.getTime))
}
def onEnd = {
val startTime = q.dequeue
}
}

Answer 3

Base from your requirements, it might be better to do it this way.
case class Job(report: List<Report>) {
def execute // does the looping on Report by calling start and call end to generate monitoring data
private def start // iterate over each Report and calls it's execute method
private def end // iterate over each Report and uses startTime and executionTime to generate monitoring data.
}
abstract class Report {
var startTime: DateTime //Time started for the report
def doReport // unimplemented method that does the report generation.
def execute // first set stateTime to Now then call doReport, lastly calculate executionTime
}
The subtype of the Report should implement the doReport which does actual reporting.
You can also change the Job.execute method to accept
report: List<Report>
so that you can have a singleton Job (For sure, start and end will be the same for all Job you have.)