Ternary conditional operator in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign the larger number to max using the ternary operator.

Swift

let max = [1] b > a ? b : a

Drag options to blanks, or click blank then click option'

A*

B+

C-

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using arithmetic operators instead of assignment.

Forgetting to assign the result to a variable.

The ternary operator returns b if b > a is true, otherwise a. The result is assigned to max using =.

2fill in blank

medium

Complete the code to print "Even" if number is even, otherwise "Odd" using the ternary operator.

Swift

print(number % 2 == 0 ? [1] : "Odd")

Drag options to blanks, or click blank then click option'

A"Odd"

B"Even"

C"Zero"

D"Number"

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the true and false values.

Using incorrect strings.

The ternary operator checks if number % 2 == 0. If true, it prints "Even", else "Odd".

3fill in blank

hard

Fix the error in the ternary expression to correctly assign the smaller value to min.

Swift

let min = [1] y < x ? y : x

Drag options to blanks, or click blank then click option'

A=

B+

C-

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using arithmetic operators instead of assignment.

Omitting the assignment operator.

The assignment operator = is needed to assign the result of the ternary expression to min.

4fill in blank

hard

Fill both blanks to create a ternary expression that assigns "Adult" if age is 18 or more, otherwise "Minor".

Swift

let status = age [1] 18 [2] "Adult" : "Minor"

Drag options to blanks, or click blank then click option'

A>=

B<

C?

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of operators.

Using wrong comparison operators.

The ternary operator syntax is condition ? trueValue : falseValue. Here, age >= 18 is the condition, so ? comes first, then the true value "Adult", then : and the false value "Minor".

5fill in blank

hard

Fill both blanks to create a ternary expression that assigns the absolute value of number to absValue.

Swift

let absValue = number [1] 0 [2] number : -number

Drag options to blanks, or click blank then click option'

A>

B?

C:

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of operators.

Using less than instead of greater than.

The ternary operator syntax is condition ? trueValue : falseValue. Here, the condition is number > 0, so ? comes first, then number if true, then : and -number if false.

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