If-else expression assignment in Kotlin - Mini Project: Build & Apply

If-else Expression Assignment in Kotlin

📖 Scenario: You are creating a simple program to decide if a person is eligible to vote based on their age.

🎯 Goal: Build a Kotlin program that uses an if-else expression to assign a message about voting eligibility.

📋 What You'll Learn

Create an age variable with a specific value

Create a variable votingMessage that uses an if-else expression to assign the correct message

Use the exact messages: "Eligible to vote" and "Not eligible to vote"

Print the votingMessage variable

💡 Why This Matters

🌍 Real World

Deciding eligibility or status based on conditions is common in apps like voting systems, age verification, or access control.

💼 Career

Understanding if-else expressions is fundamental for writing clear and concise Kotlin code in many software development roles.

1

Create the age variable

Create an age variable of type Int and set it to 20.

Kotlin

# Create an Int variable called age and set it to 20
// Your code here

Hint

Use val age: Int = 20 to create the variable.

2

Create the votingMessage variable with if-else expression

Create a variable called votingMessage and assign it using an if-else expression that sets it to "Eligible to vote" if age is 18 or more, otherwise "Not eligible to vote".

Kotlin

val age: Int = 20
# Create votingMessage using if-else expression based on age
// Your code here

Hint

Use val votingMessage = if (age >= 18) "Eligible to vote" else "Not eligible to vote".

3

Use the if-else expression to assign the message

Make sure the votingMessage variable uses the if-else expression exactly as if (age >= 18) "Eligible to vote" else "Not eligible to vote".

Kotlin

val age: Int = 20
val votingMessage = if (age >= 18) "Eligible to vote" else "Not eligible to vote"
# Confirm the if-else expression is used correctly
// Your code here

Hint

Check that the if-else expression is exactly as required.

4

Print the votingMessage

Write a println statement to print the votingMessage variable.

Kotlin

val age: Int = 20
val votingMessage = if (age >= 18) "Eligible to vote" else "Not eligible to vote"
# Print the votingMessage variable
// Your code here

Hint

Use println(votingMessage) to display the message.

Practice

1. What does the following Kotlin code do?
val result = if (score > 50) "Pass" else "Fail"

easy

A. Assigns "Pass" to result if score is greater than 50, otherwise "Fail"

B. Assigns true if score is greater than 50, otherwise false

C. Throws an error because else is missing

D. Assigns the value of score to result

Solution

1. Step 1: Understand the if-else expression

   The code uses if-else as an expression to assign a value to result based on the condition score > 50.

2. Step 2: Evaluate the condition and assignment

   If score is greater than 50, result gets "Pass"; otherwise, it gets "Fail".

3. Final Answer:

   Assigns "Pass" to result if score is greater than 50, otherwise "Fail" -> Option A

4. Quick Check:

   If-else expression assigns value based on condition [OK]

Hint: If-else expression returns a value, not just controls flow [OK]

Common Mistakes:

• Forgetting the else part causes a syntax error
• Thinking if-else is only for flow, not value assignment
• Confusing condition with assignment

2. Which of the following is the correct syntax for assigning a value using if-else expression in Kotlin?

easy

A. val x = if (a > b) 10 else 20

B. val x if (a > b) = 10 else = 20

C. val x = if a > b then 10 else 20

D. val x = if (a > b) { 10 } else { 20 } else

Solution

1. Step 1: Review Kotlin if-else expression syntax

   The correct syntax uses if(condition) value1 else value2 without extra keywords or misplaced braces.

2. Step 2: Compare options with correct syntax

   val x = if (a > b) 10 else 20 matches the correct syntax: val x = if (a > b) 10 else 20.

3. Final Answer:

   val x = if (a > b) 10 else 20 -> Option A

4. Quick Check:

   Correct if-else assignment syntax is val x = if (cond) val1 else val2 [OK]

Hint: Remember: if-else expression is inside assignment with = [OK]

Common Mistakes:

• Using 'then' keyword which Kotlin does not have
• Misplacing equals signs around else
• Adding extra else after braces

3. What is the output of this Kotlin code?

val age = 18
val status = if (age >= 18) "Adult" else "Minor"
println(status)

medium

A. Minor

B. Adult

C. 18

D. Compilation error

Solution

1. Step 1: Check the condition age >= 18

   Since age is 18, the condition age >= 18 is true.

2. Step 2: Determine the assigned value to status

   Because the condition is true, status is assigned "Adult".

3. Final Answer:

   Adult -> Option B

4. Quick Check:

   Condition true assigns "Adult" [OK]

Hint: If condition true, if-else expression returns first value [OK]

Common Mistakes:

• Assuming >= 18 is false for 18
• Printing age instead of status
• Confusing syntax causing compile error

4. Identify the error in this Kotlin code:

val x = if (num > 0) "Positive"

medium

A. Incorrect variable declaration

B. Wrong comparison operator

C. Missing else branch in if-else expression

D. No error, code is correct

Solution

1. Step 1: Check if-else expression completeness

   An if-else expression used for assignment must have both if and else branches.

2. Step 2: Identify missing else branch

   The code only has if (num > 0) "Positive" but no else part, causing a syntax error.

3. Final Answer:

   Missing else branch in if-else expression -> Option C

4. Quick Check:

   If-else expression must include else [OK]

Hint: Always include else when assigning with if-else expression [OK]

Common Mistakes:

• Omitting else branch
• Thinking if alone can assign value
• Ignoring compiler error messages

5. You want to assign a grade based on score using if-else expression assignment in Kotlin. Which code correctly assigns "A" if score >= 90, "B" if score >= 80, else "C"?

hard

A. val grade = if (score >= 90) "A" else if score >= 80 "B" else "C"

B. val grade = if (score >= 90) "A" else (score >= 80) "B" else "C"

C. val grade = if (score >= 90) { "A" } else if (score >= 80) { "B" } else { "C" } else

D. val grade = if (score >= 90) "A" else if (score >= 80) "B" else "C"

Solution

1. Step 1: Understand nested if-else expression syntax

   Kotlin allows nested if-else expressions to assign values based on multiple conditions.

2. Step 2: Check each option for correct syntax and logic

   val grade = if (score >= 90) "A" else if (score >= 80) "B" else "C" correctly nests if-else expressions with proper syntax and covers all cases.

3. Final Answer:

   val grade = if (score >= 90) "A" else if (score >= 80) "B" else "C" -> Option D

4. Quick Check:

   Nested if-else expressions assign multiple conditions [OK]

Hint: Use nested if-else expressions for multiple conditions [OK]

Common Mistakes:

• Missing parentheses in nested if
• Incorrect else placement
• Adding extra else after braces