How to access computed data from other scala file? - scala

Question

I need to access this data mapData from Calculation.scala. The way I call the function in Final.scala is as seen below.
When I see the output of fetch_data() or print it I see Future(< not completed >) and result is empty. I do not know how to wait until all data is downloaded and then access mapData? MAy I know how to do it? I am new to scala. In C++ I am aware of callbacks and handling is easy there. But in scala I a using Future, Await or OnComplete, but not clear how to do it.
Final.Scala
object finalComputation {
val calculationInfo = new Calculaton()
calclulationInfo.fetch_data()
val result = calculationInfo.getMapData()
def main(args: Array[String]): Unit = {
........
}
}
Calculation.scala
class Calculation {
var mapData = Map.empty[String, String]
def createMapData(metricItem: ActualMetrics) = {
mapData += (metricItem._1 -> metricItem._2)
}
def getMapData() = {
mapData
}
def fetch_data() = {
val totalData: Future[Done] =
querApi
.getData()
.map { data =>
(data)
}
}
}
Await.result(totalData, Duration.Inf).runForeach(unit => {
createMapData(parse.From(totalData))
})
}
}

Answer 1

Well, by starter don't mix concurrency with mutability.
Second, don't create imperative APIs that require some specific call order.
Third, Future is just a fancy wrapper over callbacks.
And fourth, don't initiate computations before the main
// file: Calculation.scala
class Calculation(queryApi: Api) {
def fetchData(): Future[Map[String, String]] =
querApi.getData().map { data =>
data.view.map { metric =>
val ActualMetrics(key, value) = parse(metric)
key -> value
}.toMap
}
}
// file: Main.scala
object Main {
def main(args: Array[String]): Unit = {
val calculation = new Calculation(...)
val dataF = calculation.fetchData()
val result = dataF.map { data =>
// Here you can process the fetched data
// It may be flatMap or foreach, instead of map;
// depending on what you want to do, check the Scaladoc
}
// I don't use future, but I think here you need to do a final await of result.
// In order to avoid the program to finish before the async computation.
}
}
I had to assume some types, but I hope this gives you a general idea of what to do.
My advice, pick any Scala course / book / tutorial and properly learn the language.