Steps

1. How to define a case class to represent a Donut object

Defining a case class is similar to defining a simple class as we've discussed in the Learn How To Create Class And Objects Tutorial. However, you also make use of the case keyword as part of the class definition.

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)

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

Use the following syntax to create instances or objects of the Donut case class.

println("\nStep 2: How to create instances or objects for the Donut case class")
val vanillaDonut: Donut = Donut("Vanilla Donut", 1.50)
val glazedDonut: Donut = Donut("Glazed Donut", 2.0)
println(s"Vanilla Donut = $vanillaDonut")
println(s"Glazed Donut = $glazedDonut")

You should see the following output when you run your Scala application in IntelliJ:

Step 2: How to create instances or objects for the Donut case class
Vanilla Donut = Donut(Vanilla Donut,1.5,None)
Glazed Donut = Donut(Glazed Donut,2.0,None)

NOTE:

• You did not have to use the new keyword when creating instances of the Donut case class.
• The case class will automatically create the Companion Object.

3. How to access fields of the Donut object

When using a case class, you do not have to write any boiler plate accessor code to be able to access the fields on objects created from a case class.

println("\nStep 3: How to access fields of the Donut object")
println(s"Vanilla Donut name field = ${vanillaDonut.name}")
println(s"Vanilla Donut price field = ${vanillaDonut.price}")
println(s"Vanilla Donut productCode field = ${vanillaDonut.productCode}")

You should see the following output when you run your Scala application in IntelliJ:

Step 3: How to access fields of the Donut object
Vanilla Donut name field = Vanilla Donut
Vanilla Donut price field = 1.5
Vanilla Donut productCode field = None

4. How to modify or update fields of the Donut object

As you have learned from the Scala Programming Features tutorial, Scala favours the use of immutability. As a results, fields defined on case class are immutable by default and as such you cannot modify them.

println("\nStep 4: How to modify or update fields of the Donut object")
// vanillaDonut.name = "vanilla donut" // compiler error. fields are immutable by default.

5. How to define the hashCode and equals method for Donut object

As mentioned earlier, when you use a case class, the Scala compiler automatically creates the hashCode and equals() methods for you.

As an example, let's create a Map to represent the type and quantity of donuts being bought by our customers. If you do not implement the hashCode method, adding and retrieving elements from the Map will give you unpredictable behaviour.

However, since we are using the case class to represent the Donut objects, the hashCode method is implemented for us!

println("\nStep 5: How to define the hashCode and equals method for Donut object")
val shoppingCart: Map[Donut, Int] = Map(vanillaDonut -> 4, glazedDonut -> 3)
println(s"All items in shopping cart = ${shoppingCart}")
println(s"Quantity of vanilla donuts in shopping cart = ${shoppingCart(vanillaDonut)}")
println(s"Quantity of glazed donuts in shopping cart = ${shoppingCart(glazedDonut)}")

You should see the following output when you run your Scala application in IntelliJ:

Step 5: How to define the hashCode and equals method for Donut object
All items in shopping cart = Map(Donut(Vanilla Donut,1.5,None) -> 4, Donut(Glazed Donut,2.0,None) -> 3)
Quantity of vanilla donuts in shopping cart = 4
Quantity of glazed donuts in shopping cart = 3