Ternary conditional operator in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the ternary conditional operator in Swift?

It is a shorthand way to write an if-else statement using the syntax: condition ? valueIfTrue : valueIfFalse.

beginner

How does the ternary operator improve code readability?

It makes simple conditional assignments or expressions shorter and easier to read by reducing multiple lines into one line.

beginner

Write a Swift example using the ternary operator to assign 'adult' or 'minor' based on age.

let status = age >= 18 ? "adult" : "minor"

intermediate

Can the ternary operator be nested in Swift? If yes, what should you be careful about?

Yes, it can be nested but it can make code hard to read and understand. Use parentheses and keep nesting minimal.

intermediate

What types of expressions can be used with the ternary conditional operator in Swift?

Any expressions that return a value can be used, as long as the true and false parts return the same type or compatible types.

What is the correct syntax of the ternary conditional operator in Swift?

A condition ? valueIfTrue : valueIfFalse

B if condition then valueIfTrue else valueIfFalse

C condition : valueIfTrue ? valueIfFalse

D condition ? valueIfFalse : valueIfTrue

The ternary operator uses the syntax: condition ? valueIfTrue : valueIfFalse.

What will this Swift code print? let age = 20; print(age >= 18 ? "Adult" : "Minor")

A Error

B Minor

C 20

D Adult

Since age is 20 which is >= 18, the condition is true, so it prints "Adult".

Can the ternary operator replace all if-else statements in Swift?

A Only for loops

B Yes, always

C No, only simple conditional expressions

D Only for functions

The ternary operator is best for simple conditions; complex logic is clearer with if-else.

What happens if the true and false expressions in a ternary operator return different types?

A Compilation error

B It will run but give wrong results

C Swift will automatically convert types

D It will ignore the false expression

Swift requires both expressions to have compatible types; otherwise, it causes a compile error.

Which of these is a good use of the ternary operator?

A Replacing complex nested if-else blocks

B Assigning a value based on a simple condition

C Writing loops

D Declaring functions

Ternary operator is ideal for simple conditional assignments, not complex logic.

Explain how the ternary conditional operator works in Swift and give a simple example.

Think of it as a short if-else that picks one of two values.

Describe when you should use the ternary operator and when to avoid it in Swift programming.

Consider how easy it is to read your code.

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