CODEWITHSUNDEEP
scalavariablesimmutability
opensas
opensas

Reputation: 63415

trying to avoid mutables in scala.. is this the right way?

I'm trying to avoid mutable variables as much as possible, but sometimes it just feels too hard, and I don't want to end with an extremely complicated code

Nevertheless I found this way to do it, but it certainly feels like cheating

I'm parsing a query, and I find find a field!value, I want to translate it to field:<>value, and then go on processing, so I came out with this code to avoid mutables, or at least to have them confined...

val (operator, negated) = {
  var operator = ConditionOperator.toConditionOperator(parsedOperator)
  var negated = parsedNegated == "!"
  // field!value => field notEqual value
  if (negated && operator == ConditionOperator.Unknown) {
    negated = false
    operator = ConditionOperator.NotEqual
  }
  (operator, negated)
}

Is this the right way to do it??? or is there a more idiomatic (and clear!) way to achieve this kind of things?

Upvotes: 1

Views: 1713

Answers (3)

Luigi Plinge
Luigi Plinge

Reputation: 51109

Well you can simplify the logic by taking negated out. Then, pattern matching is cleaner than what you had before.

val negated = parsedNegated == "!"
val operator = ConditionOperator.toConditionOperator(parsedOperator) match {
  case op if negated && op == ConditionOperator.Unknown => ConditionOperator.NotEqual
  case op => op
}

Upvotes: 1

dhg
dhg

Reputation: 52681

This is indeed cheating since var is mutable!

The way to correct this is to simply return the if-statement's result directly:

val (operator, negated) = {
  val operator = ConditionOperator.toConditionOperator(parsedOperator)
  val negated = parsedNegated == "!"
  // field!value => field notEqual value
  if (negated && operator == ConditionOperator.Unknown)
    (ConditionOperator.NotEqual, false)
  else
    (operator, negated)
}

Upvotes: 6

Rex Kerr
Rex Kerr

Reputation: 167891

The typical way to do it would be without the temporary vars either, since you don't really need them.

val operator = ConditionOperator.toConditionOperator(parsedOperator)
val negated = parsedNegated == "!"
if (!negated || operator != ConditionOperator.Unknown) (operator, negated)
else (ConditionOperator.NotEqual, false)

Upvotes: 3

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