filter and report multiple predicates

Question

This is a kind of cosmetic Scala question. A list with objects needs to be filtered on the objects\' attributes. I need to report if the first check on the attribute results

Answer 1

If you need it once, then logging an intermediate result is, probably, the simplest way. If you need this at several places, you can make the code a bit nicer using extension methods:

implicit class ListOps[+A](val list: List[A]) extends AnyVal {
    def logIfEmpty(): List[A] = {
      if (list.isEmpty) {
      println("Error: empty list") 
      // or whatever; you can even pass it as an argument
    }
    list
  }
}

Then you can use it like this:

def doFilter(list: List[Account], focusId: Int, thresHold: Float): List[Account] = list
  .filter(_.id == focusId)
  .logIfEmpty()
  .filter(_.balance >= thresHold)