Extension properties in Kotlin - Mini Project: Build & Apply

Using Extension Properties in Kotlin

📖 Scenario: Imagine you want to add a new way to get the full name of a person without changing the original Person class. Kotlin's extension properties let you do this easily.

🎯 Goal: Build a Kotlin program that uses an extension property to get the full name of a Person object by combining first and last names.

📋 What You'll Learn

Create a Person class with firstName and lastName properties

Create an extension property called fullName for the Person class

Use the fullName extension property to print the full name of a person

💡 Why This Matters

🌍 Real World

Extension properties let you add new features to existing classes, like adding a new way to get a full name, without changing the original code. This is useful when working with libraries or code you cannot modify.

💼 Career

Many Kotlin developers use extension properties to write cleaner and more readable code by extending functionality in a simple way. This skill is valuable for Android development and backend Kotlin projects.

1

Create the Person class

Create a Kotlin class called Person with two val properties: firstName and lastName, both of type String. Initialize them using the primary constructor.

Kotlin

class Person(val firstName: String, val lastName: String) {
    // Your code here
}

Need a hint?

Use class Person(val firstName: String, val lastName: String) to define the class with properties.

2

Add an extension property for fullName

Create an extension property called fullName for the Person class that returns a String. It should combine firstName and lastName separated by a space.

Kotlin

class Person(val firstName: String, val lastName: String)

// Define the extension property fullName here
// Your code here

Need a hint?

Use val Person.fullName: String get() = "$firstName $lastName" to create the extension property.

3

Create a Person object and use fullName

Create a variable called person of type Person with firstName set to "John" and lastName set to "Doe". Then create a variable called name and assign it the value of person.fullName.

Kotlin

class Person(val firstName: String, val lastName: String)

val Person.fullName: String
    get() = "$firstName $lastName"

// Create person and assign fullName to name
// Your code here

Need a hint?

Create person with Person("John", "Doe") and assign person.fullName to name.

4

Print the full name

Write a println statement to print the value of the variable name.

Kotlin

class Person(val firstName: String, val lastName: String)

val Person.fullName: String
    get() = "$firstName $lastName"

val person = Person("John", "Doe")
val name = person.fullName

// Print the full name
// Your code here

Need a hint?

Use println(name) to display the full name.