Does scala provide a default apply method for a class?
I have a class:
class Player(tea: String, sal: Int = 0) {
val team = tea
private val salary = sal
}
So no apply method here, and I haven’t defined any companion object for it, so no apply method from there too.
But I am able to do:
val player = Player("AAAA", 1000)
With no ‘new’ operator used, I understand that this line of code must invoke some apply method. But there is none defined by me. So how does it work?
>Solution :
Yes, since Scala 3, as described in the docs:
Scala case classes generate apply methods, so that values of case classes can be created using simple function application, without needing to write new.
Scala 3 generalizes this scheme to all concrete classes. Example:
class StringBuilder(s: String):
def this() = this("")
StringBuilder("abc") // old: new StringBuilder("abc")
StringBuilder() // old: new StringBuilder()
This works since a companion object with two apply methods is generated together with the class. The object looks like this:
object StringBuilder:
inline def apply(s: String): StringBuilder = new StringBuilder(s)
inline def apply(): StringBuilder = new StringBuilder()