Comments and documentation markup in Swift - Mini Project: Build & Apply

Comments and documentation markup

📖 Scenario: Imagine you are writing a simple Swift program to keep track of a book's details. You want to make sure your code is easy to understand for others and for yourself in the future.

🎯 Goal: You will create a Swift program that uses comments and documentation markup to explain what the code does. This will help anyone reading your code understand its purpose and details.

📋 What You'll Learn

Create a variable with a book title

Add a single-line comment explaining the variable

Add a multi-line comment describing the program

Use documentation markup to describe a function

💡 Why This Matters

🌍 Real World

Comments and documentation help programmers understand code quickly, especially when working in teams or returning to old projects.

💼 Career

Clear comments and documentation are essential skills for software developers to write maintainable and readable code.

1

Create a variable with a comment

Create a variable called bookTitle and set it to the string "The Swift Guide". Add a single-line comment above it that says // This is the title of the book.

Swift

# Create the variable bookTitle with a comment above
// Your code here

Hint

Use // for a single-line comment just above the variable.

2

Add a multi-line comment

Add a multi-line comment at the top of the program that says:
/* This program stores information about a book.
It uses comments to explain the code. */

Swift

/* Add a multi-line comment here explaining the program */
// This is the title of the book
var bookTitle = "The Swift Guide"

Hint

Use /* to start and */ to end a multi-line comment.

3

Add a function with documentation markup

Create a function called printBookTitle() that prints the bookTitle. Add documentation markup above the function using /// to describe that the function prints the book title.

Swift

/* This program stores information about a book.
It uses comments to explain the code. */
// This is the title of the book
var bookTitle = "The Swift Guide"

// Add the function printBookTitle() with documentation markup below
// Your code here

Hint

Use /// for documentation comments just above the function.

4

Call the function and print output

Call the function printBookTitle() to display the book title.

Swift

/* This program stores information about a book.
It uses comments to explain the code. */
// This is the title of the book
var bookTitle = "The Swift Guide"

/// Prints the book title to the console
func printBookTitle() {
    print(bookTitle)
}

// Call the function printBookTitle() below
// Your code here

Hint

Simply write printBookTitle() to call the function.

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