Chaining scope functions in Kotlin - Mini Project: Build & Apply

Chaining scope functions

📖 Scenario: You are organizing a small library system. You want to create a book record, update its details, and then display the final information.

🎯 Goal: Build a Kotlin program that creates a Book data class instance, uses chaining of scope functions to update its properties, and then prints the updated book details.

📋 What You'll Learn

Create a Book data class with title, author, and year properties

Create an instance of Book with initial values

Use chaining of scope functions apply and also to update the book's year and print a message

Print the final updated book details

💡 Why This Matters

🌍 Real World

Chaining scope functions helps write clean and readable code when updating objects and performing related actions, common in app development.

💼 Career

Understanding Kotlin scope functions and chaining is valuable for Android developers and Kotlin programmers to write concise and maintainable code.

1

Create the Book data class and initial book

Create a Kotlin data class called Book with properties title (String), author (String), and year (Int). Then create a variable myBook and assign it a Book instance with title "The Kotlin Guide", author "Anna", and year 2020.

Kotlin

data class Book(val title: String, val author: String, var year: Int)

// Create myBook instance here
// Your code here

Need a hint?

Remember to use var for year because it will change later.

2

Add a variable for the new publication year

Create a variable called newYear and set it to 2023.

Kotlin

data class Book(val title: String, val author: String, var year: Int)

val myBook = Book("The Kotlin Guide", "Anna", 2020)

// Create newYear variable here
// Your code here

Need a hint?

Just create a simple val with the number 2023.

3

Chain apply and also to update and print

Use chaining of scope functions on myBook: first use apply to update the year property to newYear, then use also to print the message "Updated book year to 2023".

Kotlin

data class Book(val title: String, val author: String, var year: Int)

val myBook = Book("The Kotlin Guide", "Anna", 2020)

val newYear = 2023

// Chain apply and also on myBook here
// Your code here

Need a hint?

Use apply to change year, then also to print the message.

4

Print the final updated book details

Write a println statement to print myBook so it shows the updated book details.

Kotlin

data class Book(val title: String, val author: String, var year: Int)

val myBook = Book("The Kotlin Guide", "Anna", 2020)

val newYear = 2023

myBook.apply {
    year = newYear
}.also {
    println("Updated book year to $newYear")
}

// Print myBook here
// Your code here

Need a hint?

Just print myBook to see the updated details.