Creating a Class in Scala

In this lesson, we will start working with object-oriented programming and you will learn how to create your own class in Scala.

We'll cover the following

Introduction

In a previous lesson, you were introduced to classes and objects. We looked at some of Scala’s built-in classes such as Seq. But you can make your own classes and, in this chapter, we will cover user-defined classes and learn how to write our very own classes and objects. We will pick up where we left off in the introductory lesson; it is recommended you go over the lesson once more before moving on.

Without further ado, let’s create our own Person class.

Defining a Class

To define a class in Scala, the class keyword is used, followed by an identifier (class name) of our choosing.

Let’s map the syntax to our Person class.

Press + to interact
class Person

At this point, our class doesn’t have any properties or methods.

Defining the Properties of a Class

Properties are variables and in Scala, they are called fields. They are also known as instance variables because every instance gets its own set of the variables.

All the members of a class, including fields, are placed in a block.

Our Person class has three fields: name, gender, and age.

Press + to interact
class Person{
  var name: String = "temp"
  var gender: String = "temp"
  var age: Int = 0
}

Make sure you define the class fields using var as the values will be reassigned for each instance of the class.

Defining the Methods of a Class

The methods of a class are executable functions which can only be used by instances of that class. Our methods are walking and talking which will simply print the name of the person that is walking or talking respectively.

Press + to interact
class Person{
  var name: String = "temp"
  var gender: String = "temp"
  var age: Int = 0
  def walking = println(s"$name is walking")
  def talking = println(s"$name is talking")
}

The methods of a class have access to the fields of the same class. This is why, in our Person class, we can use name without passing it to walking and talking.

And with this, we have created our first class with three fields and two methods. In the next lesson, we will use our Person class to create a Person object.