case class Meter(meters: Double) extends AnyVal case class Gram(grams: Double) extends AnyVal
Value classes provide a type-safe way to encode units, even if they require a bit more characters to use them:
var length = Meter(3) var weight = Gram(4) //length = weight //type mismatch; found : Gram required: Meter
AnyVals, there is no runtime penalty for using them, on the JVM level, those are regular primitive types (
Doubles in this case).
In case you want to automatically generate other units (like
MeterPerSecond), this approach is not the best, though there are libraries that can be used in those cases too: