Question

I have the following method where I want to return a map by performing a reduceLeft on a list. My issue is that occasionally the list is empty so Im not sure the correct way to deal with that:

  def results(start: String, end: String) = {
    val iter = new QueryIterator(RK, start, end);

    val list = for (hcol <- iter) yield (Map(hcol.getValue() -> 
        Map(hcol.getName()) -> hcol.getTime()))))
    list.reduceLeft(_ ++ _)
  }

When the list is empty it throws an exception that stops the execution. What is the best way to get around this problem?

Answer 1

You can use foldLeft instead and start with an empty map of the type that you want to return, e.g.

list.foldLeft(Map.empty[Int,(String,Float)])(_ ++ _)

(Make sure you properly match the type of the map; I’m guessing that getValue() returns an Int, etc..)