Elvis operator deep usage in Kotlin - Mini Project: Build & Apply

Elvis Operator Deep Usage

📖 Scenario: You are building a simple contact app that stores user information. Sometimes, some details like phone number or email might be missing. You want to use Kotlin's Elvis operator to provide default values when data is missing.

🎯 Goal: Learn how to use the Elvis operator ?: deeply in Kotlin to handle nullable values and provide fallback defaults in a real-world style contact information scenario.

📋 What You'll Learn

Create a nullable variable for phoneNumber with a null value

Create a nullable variable for email with a null value

Create a variable defaultPhone with the value "000-000-0000"

Create a variable defaultEmail with the value "[e-mail]"

Use the Elvis operator to assign contactPhone to phoneNumber or defaultPhone

Use the Elvis operator to assign contactEmail to email or defaultEmail

Use the Elvis operator deeply to assign finalContact to contactPhone if not null, else contactEmail, else the string "No contact info"

Print the finalContact value

💡 Why This Matters

🌍 Real World

Handling missing or optional user data safely is common in apps like contact managers, messaging, or user profiles.

💼 Career

Understanding Kotlin's Elvis operator helps write concise and safe code that avoids null pointer errors, a key skill for Android developers.

1

Create nullable contact details

Create a nullable variable called phoneNumber and set it to null. Also create a nullable variable called email and set it to null.

Kotlin

# Create nullable variables phoneNumber and email
// Your code here

Need a hint?

Use val phoneNumber: String? = null to create a nullable variable.

2

Create default contact values

Create a variable called defaultPhone with the value "000-000-0000". Create a variable called defaultEmail with the value "[e-mail]".

Kotlin

val phoneNumber: String? = null
val email: String? = null
# Create defaultPhone and defaultEmail variables
// Your code here

Need a hint?

Use val defaultPhone = "000-000-0000" to create a default phone string.

3

Use Elvis operator for contact fallback

Use the Elvis operator ?: to create a variable called contactPhone that is phoneNumber if not null, else defaultPhone. Also create contactEmail that is email if not null, else defaultEmail.

Kotlin

val phoneNumber: String? = null
val email: String? = null
val defaultPhone = "000-000-0000"
val defaultEmail = "[e-mail]"
# Use Elvis operator to assign contactPhone and contactEmail
// Your code here

Need a hint?

Use val contactPhone = phoneNumber ?: defaultPhone to assign with Elvis operator.

4

Use deep Elvis operator and print result

Use the Elvis operator deeply to create a variable called finalContact that is contactPhone if not null, else contactEmail, else the string "No contact info". Then print finalContact.

Kotlin

val phoneNumber: String? = null
val email: String? = null
val defaultPhone = "000-000-0000"
val defaultEmail = "[e-mail]"
val contactPhone = phoneNumber ?: defaultPhone
val contactEmail = email ?: defaultEmail
# Use deep Elvis operator to assign finalContact and print it
// Your code here

Need a hint?

Use val finalContact = contactPhone ?: contactEmail ?: "No contact info" and then println(finalContact).