Make objects with different methods in Factory Pattern - scala

Question

So I recently came across a coding technique in Scala called factory pattern, and I would like some help. Since in the example I saw, all the private classes have the same methods. My question is would it be possible to make it so that the private classes have unique methods?
abstract class Car{
// Creating four abstract methods
def bookingPrice : Double
def Brands : List[String]
def availability : Int
def book(noOfCars:Int)
}
// Creating an object
object Car{
val STANDARD = 0
val DELUXE = 1
val LUXURY = 2
// Creating private class
private class standardCar extends Car{
private var _availability = 100
override def bookingPrice = 200000
override def Brands = List("Maruti", "Tata", "Hyundai")
override def availability = _availability
override def book(noOfCars:Int) = {
_availability = _availability - noOfCars
}
}
// Creating private class
private class DeluxeCar extends Car{
private var _availability = 50
override def bookingPrice = 500000
override def Brands = List("Honda", "Mahindra", "Chevrolet")
override def availability = _availability
override def book(noOfCars:Int) = {
_availability = _availability - noOfCars
}
//enter unique method like def openSlidingDoors(){}
}
// Creating private class
private class LuxuryCar extends Car{
private var _availability = 5
override def bookingPrice = 900000
override def Brands = List("Audi","BMW", "Mercedes")
override def availability = _availability
override def book(noOfCars:Int) = {
_availability = _availability - noOfCars
}
//enter unique method like def enableFlight(){}
}
// create the apply method
// single method to create a variety of objects
def apply(carType:Int):Car = {
carType match {
case 1 => new LuxuryCar()
case 2 => new DeluxeCar()
case 3 => new standardCar()
case _ => new standardCar()
}
}
// Main method
}
object Main{
def main(args: Array[String])
{
val s = Car.apply(1)
println(s.bookingPrice)
println(s.availability)
println(s.getClass)
}
}
I tried to just slot it into the private classes and it (obviously) did not work since the methods are not part of the parent abstract class. Is there any workaround for this?

Answer 1

The concrete Car classes don't need to be private to the Car object. In fact it is better if they are not, because you can then match on the particular car that was returned to gain access to methods specific to that class (which is what you want to do).
trait Car {
def bookingPrice: Double
def Brands: List[String]
def availability: Int
def book(noOfCars: Int): Unit
}
case class StandardCar() extends Car {
private var _availability = 100
override def bookingPrice = 200000
override def Brands = List("Maruti", "Tata", "Hyundai")
override def availability = _availability
override def book(noOfCars: Int) = {
_availability = _availability - noOfCars
}
}
case class DeluxeCar() extends Car {
private var _availability = 50
override def bookingPrice = 500000
override def Brands = List("Honda", "Mahindra", "Chevrolet")
override def availability = _availability
override def book(noOfCars: Int) = {
_availability = _availability - noOfCars
}
def openSlidingDoors() = println("Open doors")
}
case class LuxuryCar() extends Car {
private var _availability = 5
override def bookingPrice = 900000
override def Brands = List("Audi", "BMW", "Mercedes")
override def availability = _availability
override def book(noOfCars: Int) = {
_availability = _availability - noOfCars
}
def enableFlight() = ???
}
// Creating an object
object Car {
val STANDARD = 0
val DELUXE = 1
val LUXURY = 2
// create the apply method
// single method to create a variety of objects
def apply(carType: Int): Car = {
carType match {
case 0 => StandardCar()
case 1 => DeluxeCar()
case 2 => LuxuryCar()
case _ => StandardCar()
}
}
// Main method
}
val s = Car.apply(1)
println(s.bookingPrice)
println(s.availability)
println(s.getClass)
s match {
case d: DeluxeCar => d.openSlidingDoors()
case _ =>
}
Using var like this is pretty ugly so prefer to create a new Car each time when updating availability, or store the availability somewhere else in the system.