Summary - Class basics
- Kotlin course
- Beginner
- Lesson 111/116
- 5 min
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.
Practice 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().
Starter code
fun main() {
// Define a Person class with a name property, greet and rename methods
// rename must use this; create an instance, call rename and greet
}Sample 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())
}Expected output
Merhaba Alex
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match tool to purpose
| Term | Meaning |
|---|---|
class |
Class |
constructor |
Constructor |
val/var |
Property |
fun |
Method |
2 What does this refer to?
- this is not used for parameters
- this gives the current object Correct answer
- this is a property
- this is always required
Explanation: this refers to the current instance.
3 Fill in the blank: assign with this
fun rename(name: String) {
____.name = name
}fun rename(name: String) {
this.name = name
}Explanation: this.name refers to the property.