Have trait like below
trait MyTrait
{
val country: String,
val state: String,
val commune: String = "nothing"
}
Now implementing MyTrait
case class ImplementTrait(
country:String,
state: String,
//commune, how to provide commune's default value if commune is not provided while initialising ImplementTrait
) extends MyTrait
For example
ImplementTrait(country, state), should work and because it will take commune default value
ImplementTrait(country, state, commune), should also work and because commune value is present now
any suggestions ?
1
I don’t think there’s something automatic that you can do easily, but you might want to consider something like the following:
object MyTrait {
val DefaultCommune = "nothing"
}
trait MyTrait {
def country: String
def state: String
def commune: String
}
final case class ImplementTrait(
country: String,
state: String,
commune: String = MyTrait.DefaultCommune,
) extends MyTrait
assert(ImplementTrait("Germany", "Bayern").commune == "nothing")
assert(ImplementTrait("Mexico", "Yucatan", "Merida").commune == "Merida")
You can play around with this code here on Scastie.
Notice a couple of changes I made to your original suggestion, as further feedback:
- No
vals intraits: you know best of course for the use case you want to cover, but in generalvals intraittend to be discouraged as the order in which you inherit traits might affect the initialization of the class (see here for more details) final case class: while you cannot inherit directly between case classes, you can have a normal class inherit from a case class — this is very unlikely something you want and might affect value semantics, which is why it’s usually recommended to make all case classes final (see here for more details)
5