Object expressions (anonymous objects) in Kotlin - Mini Project: Build & Apply

Using Object Expressions (Anonymous Objects) in Kotlin

📖 Scenario: Imagine you are building a simple notification system. You want to create a quick way to handle notifications without creating a full class for each type.

🎯 Goal: You will create an anonymous object using Kotlin's object expression to handle a notification message and display it.

📋 What You'll Learn

Create an anonymous object with a property and a function

Use the object expression to hold notification data

Call the function inside the anonymous object to display the message

💡 Why This Matters

🌍 Real World

Anonymous objects are useful when you need a quick object with some behavior but don't want to create a full class. For example, handling callbacks or simple event listeners.

💼 Career

Understanding object expressions helps you write concise Kotlin code, especially in Android development and other Kotlin-based projects where quick, temporary objects are common.

1

Create an anonymous object with a message

Create a variable called notification and assign it an anonymous object with a message property set to the string "Hello, Kotlin!".

Kotlin

// Create the anonymous object called notification with message property
// Your code here

Need a hint?

Use val notification = object { val message = "Hello, Kotlin!" } to create the anonymous object.

2

Add a function to display the message

Add a function called show inside the notification anonymous object that prints the message property.

Kotlin

val notification = object {
    val message = "Hello, Kotlin!"
    // Add function show() here
    // Your code here
}

Need a hint?

Define fun show() { println(message) } inside the object.

3

Call the show function

Call the show function on the notification object to display the message.

Kotlin

val notification = object {
    val message = "Hello, Kotlin!"
    fun show() {
        println(message)
    }
}

// Call the show() function here
// Your code here

Need a hint?

Use notification.show() to call the function.

4

Print the output

Run the program and print the output of calling notification.show().

Kotlin

val notification = object {
    val message = "Hello, Kotlin!"
    fun show() {
        println(message)
    }
}

notification.show()  // This prints the message

Need a hint?

The output should be exactly Hello, Kotlin!