Class and Objects Examples

1. How to define a simple class to represent a Donut object
scala> class Donut(name: String, productCode: Long) {
     |
     |  def print = println(s"Donut name = $name, productCode = $productCode")
     |
     | }
defined class Donut

2. How to create instances of Donut class
Step 2: How to create instances of Donut class

scala> val glazedDonut = new Donut("Glazed Donut", 1111)
glazedDonut: Donut = Donut@68e62ca4

scala> val vanillaDonut = new Donut("Vanilla Donut", 2222)
vanillaDonut: Donut = Donut@67a056f1

 How to call the print function for each of the donut object

 Step 3: How to call the print function for each of the donut object

scala> glazedDonut.print
Donut name = Glazed Donut, productCode = 1111

scala> vanillaDonut.print
Donut name = Vanilla Donut, productCode = 2222

 Companion Object
 1. How to define a simple class to represent a Donut object

scala> class Donut(name: String, productCode: Long){
     |
     |   def print = println(s"Donut name = $name, productCode = $productCode")
     |
     | }
defined class Donut

2. How to declare a companion object for the Donut class
he name of the object should be identical to the class name.

println("Step 1: How to define a simple class to represent a Donut object")
class Donut(name: String, productCode: Long){
  def print = println(s"Donut name = $name, productCode = $productCode")
}

object Donut {
 def apply(name: String, productCode: Long): Donut = {
   new Donut(name, productCode)
 }
}

// Exiting paste mode, now interpreting.
Step 1: How to define a simple class to represent a Donut object
defined class Donut
defined object Donut

Step 1: How to define a simple class to represent a Donut object
defined class Donut
defined object Donut

scala> val glazedDonut = Donut("Glazed Donut", 1111)
glazedDonut: Donut = Donut@3414a8c3

scala> val vanillaDonut = Donut("Vanilla Donut", 2222)
vanillaDonut: Donut = Donut@60cf62ad

scala> glazedDonut.print

. How to declare apply method of companion object as a factory
class GlazedDonut(name: String) extends Donut(name)
class VanillaDonut(name: String) extends Donut(name)

object Donut {
 def apply(name: String): Donut = {
  name match {
   case "Glazed Donut" => new GlazedDonut(name)
   case "Vanilla Donut" => new VanillaDonut(name)
   case _ => new Donut(name)
  }
 }
}

defined class Donut
defined class GlazedDonut
defined class VanillaDonut
defined object Donut

How to call apply method of companion object which is a factory

scala> val glazedDonut = Donut("Glazed Donut")
glazedDonut: Donut = GlazedDonut@10a18e3e

scala> println(s"The class type of glazedDonut = ${glazedDonut.getClass}")
The class type of glazedDonut = class $line28.$read$$iw$$iw$GlazedDonut

scala> glazedDonut.print
Donut name = Glazed Donut, productCode = 0
scala>

scala> val vanillaDonut = Donut("Vanilla Donut")
vanillaDonut: Donut = VanillaDonut@9e02f84

scala> println(s"The class type of vanillaDonut = ${vanillaDonut.getClass}")
The class type of vanillaDonut = class $line28.$read$$iw$$iw$VanillaDonut

scala> vanillaDonut.print
Donut name = Vanilla Donut, productCode = 0

scala> :paste
// Entering paste mode (ctrl-D to finish)
println("Step 1: How to define a simple class to represent a Donut object")
class Donut(name: String, productCode: Option[Long] = None){
def print = println(s"Donut name = $name, productCode = ${productCode.getOrElse(0)}, uuid = ${Donut.uuid}")
}
println("\nStep 2: How to declare fields and values in companion object")
object Donut {
 private val uuid = 1
 def apply(name: String, productCode: Option[Long]): Donut = {
  new Donut(name, productCode)
 }
 def apply(name: String): Donut = {
  new Donut(name)
 }
}

// Exiting paste mode, now interpreting.
Step 1: How to define a simple class to represent a Donut object
Step 2: How to declare fields and values in companion object
defined class Donut
defined object Donut

scala>

scala> println("\nStep 3: How to create instances of the Donut class using the companion object")

Step 3: How to create instances of the Donut class using the companion object

scala> val glazedDonut = Donut("Glazed Donut", Some(1111))
glazedDonut: Donut = Donut@3ea75b05

scala> val vanillaDonut = Donut("Vanilla Donut")
vanillaDonut: Donut = Donut@63a7781

scala> glazedDonut.print

Donut name = Glazed Donut, productCode = 1111, uuid = 1

scala> vanillaDonut.print
Donut name = Vanilla Donut, productCode = 0, uuid = 1

1. How to declare a Singleton Object
scala> object DonutShoppingCartCalculator {
     |
     |  println("\nStep 2: How to define a global field")
     |  val discount: Double = 0.01
     |
     |  println("\nStep 3: How to define utility function called calculateTotalCost")
     |  def calculateTotalCost(donuts: List[String]): Double = {
     |   // calculate the cost of donuts
     |   return 1
     |  }
     | }
defined object DonutShoppingCartCalculator

scala> println(s"Global discount = ${DonutShoppingCartCalculator.discount}")

Step 2: How to define a global field
Step 3: How to define utility function called calculateTotalCost
Global discount = 0.01


scala> println(s"Call to calculateTotalCost function = ${DonutShoppingCartCalculator.calculateTotalCost(List())}")
Call to calculateTotalCost function = 1.0

println("Step 1: How to define a case class to represent a Donut object")

case class Donut(name: String, price: Double, productCode: Option[Long] = None)

Step 2: How to create instances or objects for the Donut case class

scala> val vanillaDonut: Donut = Donut("Vanilla Donut", 1.50)
vanillaDonut: Donut = Donut(Vanilla Donut,1.5,None)

scala> val glazedDonut: Donut = Donut("Glazed Donut", 2.0)
glazedDonut: Donut = Donut(Glazed Donut,2.0,None)

scala> println(s"Vanilla Donut = $vanillaDonut")
Vanilla Donut = Donut(Vanilla Donut,1.5,None)

scala> println(s"Glazed Donut = $glazedDonut")
Glazed Donut = Donut(Glazed Donut,2.0,None)

scala> println(s"Vanilla Donut name field = ${vanillaDonut.name}")
Vanilla Donut name field = Vanilla Donut

scala> println(s"Vanilla Donut price field = ${vanillaDonut.price}")
Vanilla Donut price field = 1.5

scala> println(s"Vanilla Donut productCode field = ${vanillaDonut.productCode}")
Vanilla Donut productCode field = None

Step 5: How to define the hashCode and equals method for Donut object
scala> val shoppingCart: Map[Donut, Int] = Map(vanillaDonut -> 4, glazedDonut -> 3)
shoppingCart: Map[Donut,Int] = Map(Donut(Vanilla Donut,1.5,None) -> 4, Donut(Glazed Donut,2.0,None) -> 3)

scala> println(s"All items in shopping cart = ${shoppingCart}")
All items in shopping cart = Map(Donut(Vanilla Donut,1.5,None) -> 4, Donut(Glazed Donut,2.0,None) -> 3)

scala> println(s"Quantity of vanilla donuts in shopping cart = ${shoppingCart(vanillaDonut)}")
Quantity of vanilla donuts in shopping cart = 4

scala> println(s"Quantity of glazed donuts in shopping cart = ${shoppingCart(glazedDonut)}")
Quantity of glazed donuts in shopping cart = 3

Abstract Class:
scala>  abstract class Donut(name: String) {
     |
     |    def printName: Unit
     |
     | }
defined class Donut

warning: previously defined object Donut is not a companion to class Donut.
Companions must be defined together; you may wish to use :paste mode for this.

scala> :paste
// Entering paste mode (ctrl-D to finish)
 class VanillaDonut(name: String) extends Donut(name) {
   override def printName: Unit = println(name)
 }
 object VanillaDonut {
   def apply(name: String): Donut = {
     new VanillaDonut(name)
   }
}
// Exiting paste mode, now interpreting.
defined class VanillaDonut
defined object VanillaDonut

scala> :paste
// Entering paste mode (ctrl-D to finish)
println("\nStep 3: How to extend abstract class Donut and define another sub-class of Donut called GlazedDonut")
 class GlazedDonut(name: String) extends Donut(name) {
   override def printName: Unit = println(name)
 }
 object GlazedDonut {
   def apply(name: String): Donut = {
     new GlazedDonut(name)
   }
 }
// Exiting paste mode, now interpreting.

Step 3: How to extend abstract class Donut and define another sub-class of Donut called GlazedDonut
defined class GlazedDonut
defined object GlazedDonut

scala> val vanillaDonut: Donut = VanillaDonut("Vanilla Donut")
vanillaDonut: Donut = VanillaDonut@66709528

scala> vanillaDonut.printName
Vanilla Donut
scala>
scala> val glazedDonut: Donut = GlazedDonut("Glazed Donut")
glazedDonut: Donut = GlazedDonut@10742c78

scala> glazedDonut.printName
Glazed Donut
scala>