Methods

Learn to define methods in a class.

Methods: behaviour of a class

A method is a function defined inside a class. It is called on an instance and can access the properties.

class Person(val name: String) {
    fun greet() = "Hello $name"
}

val p = Person("Alex")
println(p.greet())  // Hello Alex

A method is behaviour attached to an instance; $name uses the property directly. The call p.greet() runs the method and returns the result. This keeps data and behaviour in one place.

Calling a method

You call a method on an instance with a dot. The method can access the instance's properties directly.

val p = Person("Alex")
val message = p.greet()
println(message)

p.greet() runs the method and returns a value. You can assign the result to a variable or print it directly. The parentheses mark the method call.

Exercise Add a greet method to Person

Define class Person(val name: String); in its body write fun greet() = "Hello $name". In main create val p = Person("Alex") and print p.greet() with println.

Show example solution

class Person(val name: String) {
    fun greet() = "Hello $name"
}

fun main() {
    val p = Person("Alex")
    println(p.greet())
}

Test yourself

What is a fun inside a class called?
- A function outside the class
- A property
- A constant
- A function defined inside the class
Show answer

A function defined inside the class — A function inside a class is a method.
Match concept to role

fun greet()

Method
val name

Property
class Person

Class
Person("Alex")

Instance

Fill in the blank: call the method

val p = Person("Alex")
val message = p.____()

Show answer

val p = Person("Alex")
val message = p.greet()

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