我怎样才能在不重复的情况下以功能方式正确编写此代码

Question

在下面的函数中，我传递了一个 Option。根据 Option 是 Some 还是 None，我需要调用特定的 API，但其余代码对于两者都是相同的 Some和 None。我不知道如何删除代码重复。我怎样才能以函数式编程风格重写代码？

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)
        }    
      }
}

Answer 1

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)
  }
}

Answer 2

知道了。我忘记了 Scala returns 中的所有值，甚至 match，所以我可以这样做

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
  }
}

我怎样才能在不重复的情况下以功能方式正确编写此代码

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

functional-programming

scala

option