How could I correctly write this code in functional way without duplication

Question

In the following function, I am passing an Option. Depending on whether the Option is Some or None, I need to call the a specific API but the rest of the code is the same for both Some and None. I don't know how to remove the code duplication though. How could I re-write the code in functional-programming style?

def getRowsByPartitionKeyId(id:I, pagingStateOption:Option[PagingState]):Tuple2[Option[List[M]],Option[PagingState]] = {
    pagingStateOption match {
      case Some(pagingState:PagingState) => {

        val resultSet = session.execute(whereClause
          .setFetchSize(1)
          .setPagingState(pagingState)) //THIS IS THE ONLY DIFFERENCE IN THE TWO CODE LEGS


        val it = resultSet.iterator();//resultSet is an iterator
        val newPagingState:PagingState = resultSet.getExecutionInfo.getPagingState


        if(it.hasNext){


          val resultSetAsList:List[Row] = asScalaIterator(it).toList
          val resultSetAsModelList = rowToModel(resultSetAsList.head)


          Tuple2(Some(List(resultSetAsModelList)),Some(pagingState))
        }
        else {
          Tuple2(None, None)
        }
      }
      case None =>{
        val resultSet = session.execute(whereClause
          .setFetchSize(1)) //get one row from ResultSet. Cassandra might return more or less though

        val it = resultSet.iterator();//resultSet is an iterator
        val pagingState:PagingState = resultSet.getExecutionInfo.getPagingState


        if(it.hasNext){


          val resultSetAsList:List[Row] = asScalaIterator(it).toList
          val resultSetAsModelList = rowToModel(resultSetAsList.head)


          Tuple2(Some(List(resultSetAsModelList)),Some(pagingState))
        }
        else {
          Tuple2(None, None)
        }    
      }
}

Andrey Tyukin · Accepted Answer · 2018-07-13 17:24:06Z

2

def getRowsByPartitionKeyId(
  id:I, 
  pagingStateOption:Option[PagingState]
): (Option[List[M]], Option[PagingState]) = {

  val resultSet = session.execute(pagingStateOption match {
    case Some(pagingState: PagingState) => 
      whereClause.setFetchSize(1).setPagingState(pagingState)
    case None =>
      whereClause.setFetchSize(1)
  })

  val it = resultSet.iterator();//resultSet is an iterator
  val newPagingState:PagingState = resultSet.getExecutionInfo.getPagingState


  if (it.hasNext) {


    val resultSetAsList:List[Row] = asScalaIterator(it).toList
    val resultSetAsModelList = rowToModel(resultSetAsList.head)


    Tuple2(Some(List(resultSetAsModelList)),Some(pagingState))
  } else {
    Tuple2(None, None)
  }
}

answered Jul 13, 2018 at 17:24

Andrey Tyukin

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Comments

Manu Chadha · Accepted Answer · 2018-07-13 17:24:23Z

0

Got it. I forgot that everything in Scala returns a value, even match, so I can do this

val resultSet = pagingStateOption match {
  case Some(pagingState: PagingState) => {
    println("got paging state:" +pagingState)
    session.execute(whereClause
      .setFetchSize(1)
      .setPagingState(pagingState)) //get one row from ResultSet. Cassandra might return more or less though
  }
  case None => {
    session.execute(whereClause
      .setFetchSize(1)) //get one row from ResultSet. Cassandra might return more or less though
  }
}

answered Jul 13, 2018 at 17:24

Manu Chadha

16.9k28 gold badges121 silver badges258 bronze badges

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