Defining Classes | Classes And Objects

Introduction to Classes

In Kotlin, a class is a blueprint for creating objects. A class encapsulates data for the object and methods to manipulate that data. This tutorial will guide you through the process of defining classes in Kotlin, covering the syntax, properties, methods, and more.

Basic Syntax of a Class

To define a class in Kotlin, you use the class keyword followed by the class name. Here’s a simple example:

class Car { }

This defines an empty class named Car. Classes can contain properties and methods, which we will explore next.

Adding Properties to a Class

Properties are variables that hold data related to the class. You can define properties directly in the class body. Here’s how to do it:

class Car(val make: String, val model: String, var year: Int) { }

In this example, make and model are read-only properties (defined with val), while year is a mutable property (defined with var).

Defining Methods in a Class

Methods are functions defined within a class that can operate on the properties of that class. You can define methods to perform actions or calculations. Here’s an example:


                    class Car(val make: String, val model: String, var year: Int) {
                        fun displayInfo() {
                            println("Car: $make $model, Year: $year")
                        }
                    }

The displayInfo method prints the car's details. You can call this method on an instance of the class.

Creating an Instance of a Class

To use a class, you create an instance (or object) of it. Here’s how to create an instance of the Car class:

val myCar = Car("Toyota", "Corolla", 2020)

This creates a new Car object with the specified properties. You can then call the displayInfo method on this object:

myCar.displayInfo()

Output: Car: Toyota Corolla, Year: 2020

Constructor in Kotlin

The primary constructor is part of the class header and is a concise way to initialize an object. For example:


                    class Car(val make: String, val model: String, var year: Int)

This single line defines both the class and its properties. You can also define a secondary constructor if needed.

Conclusion

Defining classes in Kotlin is straightforward and allows for the encapsulation of data and functionality. You can create properties, define methods, and instantiate objects easily. Understanding how to define classes is fundamental to object-oriented programming in Kotlin, paving the way for more complex programming concepts.

Defining Classes in Kotlin