Comments and documentation markup in Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of comments in Swift code?

Comments explain the code to humans. They help others (and yourself) understand what the code does without affecting how the program runs.

beginner

How do you write a single-line comment in Swift?

Use two slashes // before the comment text. Everything after // on that line is ignored by the compiler.

beginner

How do you write a multi-line comment in Swift?

Start with /* and end with */. Everything between is treated as a comment, even if it spans many lines.

intermediate

What is documentation markup in Swift and why is it useful?

Documentation markup uses special comment styles (like ///) to create structured notes. These notes can be shown in code editors to explain functions, parameters, and return values clearly.

intermediate

Give an example of a documentation comment for a Swift function.

/// Adds two numbers and returns the result.
/// - Parameters:
///   - a: The first number.
///   - b: The second number.
/// - Returns: The sum of a and b.

Which symbol starts a single-line comment in Swift?

A #

B //

C /*

D <!--

Single-line comments in Swift start with //. Multi-line comments use /* ... */.

What does the following Swift comment style /// indicate?

A A compiler directive

B A single-line comment

C A multi-line comment start

D A documentation comment for code explanation

/// is used for documentation comments that provide structured information about code elements.

How do multi-line comments behave in Swift?

A They start with <code>/*</code> and end with <code>*/</code>

B They start with <code>//</code> and end with a blank line

C They start with <code>///</code> and end with <code>///</code>

D They start with <code>#</code> and end with <code>#</code>

Multi-line comments in Swift are enclosed between /* and */.

Why should you use documentation comments in your Swift code?

A To help others understand your code with clear explanations

B To make the code run faster

C To hide code from the compiler

D To change the code's logic

Documentation comments improve code readability and help others (and yourself) understand how to use your code.

Which of these is NOT a valid Swift comment style?

A /// This is a documentation comment

B /* This is a comment */

C <!-- This is a comment -->

D // This is a comment

is an HTML comment style, not valid in Swift.

Explain the difference between single-line, multi-line, and documentation comments in Swift.

Think about how each comment type looks and what it is used for.

Write a documentation comment for a Swift function that multiplies two numbers and returns the result.

Follow the Swift documentation comment format with clear sections.

Practice

1. What is the main purpose of comments in Swift code?

easy

A. To create new variables

B. To make the code run faster

C. To explain the code for better understanding

D. To store user data

Solution

1. Step 1: Understand what comments do

   Comments are notes in the code that do not affect how the program runs but help explain what the code does.

2. Step 2: Identify the purpose of comments

   Comments make the code easier to read and understand for yourself and others who read the code later.

3. Final Answer:

   To explain the code for better understanding -> Option C

4. Quick Check:

   Comments explain code [OK]

Hint: Comments explain code, not run it or store data [OK]

Common Mistakes:

• Thinking comments speed up code
• Confusing comments with variables
• Using comments to store data

2. Which of the following is the correct syntax for a single-line comment in Swift?

easy

A. # This is a comment

B. /* This is a comment */

C.

D. // This is a comment

Solution

1. Step 1: Recall Swift comment syntax

   Swift uses // for single-line comments and /* */ for multi-line comments.

2. Step 2: Match the correct syntax

   // This is a comment uses // which is the correct single-line comment syntax in Swift.

3. Final Answer:

   // This is a comment -> Option D

4. Quick Check:

   Single-line comment = // [OK]

Hint: Single-line comments start with // in Swift [OK]

Common Mistakes:

• Using /* */ for single-line comments
• Using HTML style comments
• Using # which is not a comment in Swift

3. What will the following Swift code output?

/// Adds two numbers
func add(_ a: Int, _ b: Int) -> Int {
    return a + b
}
print(add(3, 4))

medium

A. 7

B. add(3, 4)

C. /// Adds two numbers

D. Error: Unexpected documentation comment

Solution

1. Step 1: Understand documentation comments effect

   The line starting with /// is a documentation comment and does not affect the code execution.

2. Step 2: Execute the function call

   The function add returns the sum of 3 and 4, which is 7, and print outputs it.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   Documentation comment ignored, output = 7 [OK]

Hint: Documentation comments don't change output, only explain [OK]

Common Mistakes:

• Thinking documentation comments print text
• Expecting error from documentation comments
• Confusing comments with code

4. Identify the error in this Swift code snippet:

/* This is a multi-line comment
func greet() {
    print("Hello")
}
// Missing closing comment delimiter

medium

A. Using // inside multi-line comment is invalid

B. Missing closing */ for multi-line comment

C. Function greet() is not declared properly

D. print statement syntax error

Solution

1. Step 1: Check multi-line comment syntax

   Multi-line comments start with /* and must end with */ to close properly.

2. Step 2: Identify missing closing delimiter

   The code has /* but no closing */, so the comment never ends, causing a syntax error.

3. Final Answer:

   Missing closing */ for multi-line comment -> Option B

4. Quick Check:

   Multi-line comment must close with */ [OK]

Hint: Multi-line comments need /* and */ to open and close [OK]

Common Mistakes:

• Ignoring missing closing comment delimiter
• Thinking // can't be inside multi-line comments
• Assuming function syntax is wrong

5. You want to document a Swift function so that Xcode shows its description and parameters clearly. Which comment style should you use?

func multiply(_ x: Int, _ y: Int) -> Int {
    return x * y
}

hard

A. /// Multiplies two numbers
/// - Parameters:
/// - x: The first number
/// - y: The second number
/// - Returns: The product of x and y

B. /* Multiplies two numbers */

C. // This function multiplies two numbers

D.

Solution

1. Step 1: Understand documentation comment usage

   Documentation comments in Swift use /// and special markup to describe functions and parameters for tools like Xcode.

2. Step 2: Identify the detailed documentation style

   /// Multiplies two numbers /// - Parameters: /// - x: The first number /// - y: The second number /// - Returns: The product of x and y uses /// with - Parameters and - Returns tags, which is the correct way to document for Xcode's quick help.

3. Final Answer:

   /// Multiplies two numbers /// - Parameters: /// - x: The first number /// - y: The second number /// - Returns: The product of x and y -> Option A

4. Quick Check:

   Use /// with parameter tags for documentation [OK]

Hint: Use /// with - Parameters and - Returns for Xcode docs [OK]

Common Mistakes:

• Using single-line or multi-line comments without markup
• Using HTML style comments
• Not including parameter descriptions