Summary - Class basics

Combine class, constructor and methods to write a User class.

Summary - Class basics

In this group you learned to declare a new type with class, create properties with the primary constructor, use val/var properties, write methods inside a class and resolve parameter-property clashes with this.

Now it is time to combine them in a small task: add a property, a method and a rename method using this to a class. This is a small sample of a real class design.

Exercise Add rename and greet to Person

Define class Person(var name: String); in its body add fun greet() = "Hello $name" and fun rename(name: String) { this.name = name }. In main create val p = Person("Alex"), call p.rename("Ayşe") and print p.greet().

Show example solution

class Person(var name: String) {
    fun greet() = "Hello $name"
    fun rename(name: String) {
        this.name = name
    }
}

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

Test yourself

Match tool to purpose

class

Class
constructor

Constructor
val/var

Property
fun

Method
What does this refer to?
- this is not used for parameters
- this gives the current object
- this is a property
- this is always required
Show answer

this gives the current object — this refers to the current instance.

Fill in the blank: assign with this

fun rename(name: String) {
    ____.name = name
}

Show answer

fun rename(name: String) {
    this.name = name
}

Next lesson: Project design

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