CODEWITHSUNDEEP
scala
Jake
Jake

Reputation: 4650

Scala: "Never use return statement" but

I am very new to Scala and still trying to get my head around it. (I am coming from Java mostly).

I have a question about the convention/rule that we should never use the return statement.

I have a function that creates a LabeledPoint object. The last line creates the LabeledPoint. It is not an expression, so the compiler thinks the previous line of code (which functions as a Unit) should be returned. However, the function signature is, of course, returning LabeledPoint, ergo compilation error.

if I add a return statement, all is well.

Here is the code:

@throws(classOf[Exception])
private def convertRowToLabeledPoint(rowIn: Row, fieldNameSeq: Seq[String], label:Int)
: LabeledPoint =
  {
  try
  {


  val values: Map[String, Integer] = rowIn.getValuesMap(fieldNameSeq)

  val sortedValuesMap = ListMap(values.toSeq.sortBy(_._1): _*)

  //println(s"convertRowToLabeledPoint row values ${sortedValuesMap}")
  print(".")

  val rowValuesItr: Iterable[Integer] = sortedValuesMap.values

  var positionsArray: ArrayBuffer[Int] = ArrayBuffer[Int]()
  var valuesArray: ArrayBuffer[Double] = ArrayBuffer[Double]()
  var currentPosition: Int = 0
  rowValuesItr.foreach
  {
    kv =>
      if (kv > 0)
      {
        valuesArray += kv.doubleValue();
        positionsArray += currentPosition;
      }
      currentPosition = currentPosition + 1;
  }

  val lp:LabeledPoint = new LabeledPoint(label,  org.apache.spark.mllib.linalg.Vectors.sparse(positionsArray.size,positionsArray.toArray, valuesArray.toArray))

  return lp


}
catch
{
  case ex: Exception =>
  {
    throw new Exception(ex)
  }
}

}

So, how do I switch out my Java brain and reshape (or break up) this function? Or is it OK to use return here?

Upvotes: 1

Views: 99

Answers (3)

Alexey Romanov
Alexey Romanov

Reputation: 170713

Or, if you want lp variable e.g. for debugging,

val lp = ...

lp

Upvotes: 1

S.Karthik
S.Karthik

Reputation: 1389

The last line should be 

new LabeledPoint(label,  org.apache.spark.mllib.linalg.Vectors.sparse(positionsArray.size,positionsArray.toArray, valuesArray.toArray))

That is enough. val lp:LabeledPoint = new LabeledPoint(..) is assignment statement, so the compiler still expecting return type

Upvotes: 5

delta
delta

Reputation: 3818

replace

val lp:LabeledPoint = new LabeledPoint(label,  org.apache.spark.mllib.linalg.Vectors.sparse(positionsArray.size,positionsArray.toArray, valuesArray.toArray))

return lp

with

new LabeledPoint(label,  org.apache.spark.mllib.linalg.Vectors.sparse(positionsArray.size,positionsArray.toArray, valuesArray.toArray))

The last expression is the return value of the function.

Upvotes: 2

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