Ternary conditional operator in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple ternary expression

What is the output of this Swift code?

Swift

let a = 10
let b = 20
let result = a > b ? "a is greater" : "b is greater"
print(result)

A a is greater

B b is greater

C true

D false

💡 Hint

Compare the values of a and b carefully.

Since 10 is not greater than 20, the condition is false, so the else part "b is greater" is chosen.

❓ Predict Output

intermediate

Ternary operator with numeric result

What will be printed by this Swift code?

Swift

let x = 5
let y = 8
let max = x > y ? x : y
print(max)

A 8

B false

C true

D 5

💡 Hint

Check which number is bigger.

Since 5 is not greater than 8, the else part y (8) is assigned to max.

❓ Predict Output

advanced

Nested ternary conditional output

What is the output of this Swift code?

Swift

let score = 75
let grade = score >= 90 ? "A" : score >= 80 ? "B" : score >= 70 ? "C" : "F"
print(grade)

A A

B B

C F

D C

💡 Hint

Evaluate conditions from left to right.

75 is not >= 90 or 80, but it is >= 70, so grade is "C".

❓ Predict Output

advanced

Ternary operator with Boolean result

What does this Swift code print?

Swift

let isSunny = false
let activity = isSunny ? "Go outside" : "Stay inside"
print(activity)

A Stay inside

B Go outside

C true

D false

💡 Hint

Check the Boolean value of isSunny.

Since isSunny is false, the else part "Stay inside" is chosen.

❓ Predict Output

expert

Complex ternary with side effects

What is the output of this Swift code?

Swift

var count = 0
let result = count == 0 ? "Zero" : { count += 1; return "Not zero" }()
print(result)
print(count)

A Compilation error

B Not zero and then 1

C Zero and then 0

D Zero and then 1

💡 Hint

Notice when the closure is executed.

Since count == 0 is true, the first string "Zero" is assigned and the closure is not executed, so count stays 0.

Practice

1. What does the ternary conditional operator do in Swift?
condition ? valueIfTrue : valueIfFalse

easy

A. Declares a constant value

B. Repeats a block of code multiple times

C. Defines a new function

D. Chooses one of two values based on a condition

Solution

1. Step 1: Understand the operator structure

   The ternary operator uses a condition followed by a question mark, then two values separated by a colon.

2. Step 2: Identify its purpose

   It selects the first value if the condition is true, otherwise the second value.

3. Final Answer:

   Chooses one of two values based on a condition -> Option D

4. Quick Check:

   Ternary operator = chooses between two values [OK]

Hint: Remember: condition ? trueValue : falseValue picks one [OK]

Common Mistakes:

• Confusing ternary with loops
• Thinking it declares variables
• Mixing it with function syntax

2. Which of the following is the correct syntax for the ternary conditional operator in Swift?

easy

A. condition ? valueIfTrue : valueIfFalse

B. condition : valueIfTrue ? valueIfFalse

C. condition ? (valueIfTrue, valueIfFalse)

D. condition ? valueIfTrue; valueIfFalse

Solution

1. Step 1: Recall the ternary syntax

   The correct syntax places the condition first, then a question mark, then the true value, a colon, and the false value.

2. Step 2: Compare options

   Only condition ? valueIfTrue : valueIfFalse matches this exact pattern.

3. Final Answer:

   condition ? valueIfTrue : valueIfFalse -> Option A

4. Quick Check:

   Syntax is condition ? true : false [OK]

Hint: Question mark before colon is key in ternary syntax [OK]

Common Mistakes:

• Swapping question mark and colon
• Using commas instead of colon
• Adding semicolons inside ternary

3. What is the output of this Swift code?

let age = 20
let canVote = age >= 18 ? "Yes" : "No"
print(canVote)

medium

A. No

B. Yes

C. true

D. false

Solution

1. Step 1: Evaluate the condition

   age is 20, which is greater than or equal to 18, so the condition is true.

2. Step 2: Apply ternary operator

   Since the condition is true, canVote is assigned "Yes".

3. Final Answer:

   Yes -> Option B

4. Quick Check:

   age >= 18 is true, so output is "Yes" [OK]

Hint: Check condition result first, then pick true or false value [OK]

Common Mistakes:

• Confusing true and false branches
• Assuming boolean output instead of string
• Ignoring the condition value

4. Identify the error in this Swift code using the ternary operator:

let score = 85
let grade = score > 90 ? "A" : "B" else "C"

medium

A. Using double quotes instead of single quotes

B. Missing parentheses around condition

C. Extra 'else' keyword after ternary operator

D. Incorrect variable declaration

Solution

1. Step 1: Analyze ternary operator usage

   The ternary operator already includes both true and false values separated by a colon; adding 'else' is invalid syntax.

2. Step 2: Identify the syntax error

   The 'else' keyword after the ternary expression causes a syntax error.

3. Final Answer:

   Extra 'else' keyword after ternary operator -> Option C

4. Quick Check:

   No 'else' after ternary operator [OK]

Hint: Ternary uses colon, never 'else' keyword [OK]

Common Mistakes:

• Adding 'else' after ternary
• Confusing ternary with if-else blocks
• Misplacing colons and question marks

5. Given a dictionary of student scores, use a ternary operator in Swift to create a new dictionary that marks each student as "Pass" if their score is 50 or more, otherwise "Fail".
What is the correct way to write this using dictionary comprehension?

let scores = ["Anna": 75, "Ben": 45, "Cara": 50]
let results = scores.mapValues { score in
    // Fill in here
}

hard

A. score >= 50 ? "Pass" : "Fail"

B. if score >= 50 { "Pass" } else { "Fail" }

C. score > 50 ? "Pass" : "Fail"

D. score >= 50 ? "Fail" : "Pass"

Solution

1. Step 1: Understand the condition for passing

   Students pass if their score is 50 or more, so condition is score >= 50.

2. Step 2: Apply ternary operator correctly

   Use ternary to return "Pass" if true, else "Fail".

3. Final Answer:

   score >= 50 ? "Pass" : "Fail" -> Option A

4. Quick Check:

   Use condition ? "Pass" : "Fail" for mapping [OK]

Hint: Use mapValues with ternary: condition ? trueVal : falseVal [OK]

Common Mistakes:

• Using if-else instead of ternary in mapValues
• Wrong comparison operator (>)
• Swapping Pass and Fail values