In contrast to Java, all values in Scala are objects (including numerical values and functions). Since Scala is class-based, all values are instances of a class.
Class hierarchy is linear, a class can only extend from one parent class:
class Soldier(val firstName: String, val lastName: String) {}
class Pilot(override val firstName: String, override val lastName: String, val squadron: Long)
extends Soldier(firstName, lastName)
val pilot = new Pilot("John", "Yossarian", 256)
pilot.firstName should be(res0)
pilot.lastName should be(res1)
A class that extends from another is polymorphic:
class Soldier(val firstName: String, val lastName: String) {}
class Pilot(override val firstName: String, override val lastName: String, val squadron: Long)
extends Soldier(firstName, lastName)
val pilot = new Pilot("John", "Yossarian", 256)
val soldier: Soldier = pilot
soldier.firstName should be(res0)
soldier.lastName should be(res1)
An abstract class, as in Java, cannot be instantiated and only inherited:
abstract class Soldier(val firstName: String, val lastName: String) {}
// if you uncomment this line, it will fail compilation
//val soldier = new Soldier
A class can be placed inside an abstract class just like in Java:
abstract class Soldier(val firstName: String, val lastName: String) {
class Catch(val number: Long) {
// nothing to do here. Just observe that it compiles
}
}
class Pilot(override val firstName: String, override val lastName: String, val squadron: Long)
extends Soldier(firstName, lastName)
val pilot = new Pilot("John", "Yossarian", 256)
val catchNo =
new pilot.Catch(22) //using the pilot instance's path, create an catch object for it.
catchNo.number should be(res0)
