Commenting in Swift

In Swift, comments are used to add notes or explanations within the code, making it easier to understand. Swift supports two types of comments: single-line and multi-line comments. Here’s a detailed explanation of both:

Single-line Comments

Single-line comments start with two forward slashes (//). Everything after // on that line is considered a comment and is ignored by the compiler.

// This is a single-line comment
let message = "Hello, world!" // This comment is at the end of a line of code

In the example above:

• The first line is a comment explaining something about the code.
• The comment after the variable declaration provides additional context about the code on that line.

Multi-line Comments

Multi-line comments start with /* and end with */. Everything between these markers is considered a comment and is ignored by the compiler. Multi-line comments can span multiple lines.

/* This is a multi-line comment.
   It can span multiple lines.
   This is useful for longer explanations or documentation. */
let message = "Hello, world!"

Nested Comments

Swift supports nested multi-line comments. This means you can place one multi-line comment inside another.

/* This is the outer comment.
   /* This is a nested comment. */
   This is still part of the outer comment. */
let message = "Hello, world!"

Documentation Comments

Swift also supports documentation comments, which are used to generate documentation for your code. Documentation comments start with /// for single-line or /** ... */ for multi-line comments. These comments can be processed by documentation tools to create reference material for your code.

Example (Single-line Documentation Comment):

/// This function prints a sayHello message to the console.
func sayHello() {
    print("Hello, world!")
}

Example (Multi-line Documentation Comment):

/**
 This function prints a greeting message to the console.

 - Parameters:
    - name: The name to include in the greeting.
 */
func sayHello(name: String) {
    print("Hello, \(name)!")
}

In the examples above:

• The single-line documentation comment provides a brief description of the greet function.
• The multi-line documentation comment provides a more detailed description, including information about the function’s parameters.

TODO Comments

TODO comments are used to indicate areas of the code that need further work or improvements. These comments help developers keep track of tasks that need to be addressed but are not immediately critical.

// TODO: Implement error handling for network requests
func fetchData() {
    // Code for fetching data
}

Best Practices for TODO Comments:

1. Be Specific: Provide clear and detailed information about what needs to be done.
2. Include Context: Explain why the task is necessary, if it’s not immediately obvious.
3. Prioritize: Optionally, include a priority level or a due date.

FIXME Comments

FIXME comments are used to mark parts of the code that are known to be problematic or broken. These comments serve as reminders that the code needs to be fixed as soon as possible.

// FIXME: This function fails when input is null
func processInput(input: String?) {
    // Current implementation
}

Best Practices for FIXME Comments:

1. Describe the Issue: Clearly state what is wrong with the code.
2. Provide Guidance: Suggest potential fixes or approaches to solve the problem.
3. Use Judiciously: Reserve FIXME for issues that are critical and need prompt attention.

NOTE Comments

NOTE comments are used to add important notes or observations about the code that might not fit under TODO or FIXME. These comments can provide valuable context or highlight significant points.

// NOTE: This algorithm assumes the input array is sorted
func searchArray(array: [Int], target: Int) -> Int? {
    // Search logic
}

Best Practices for NOTE Comments:

1. Highlight Important Information: Use NOTE to emphasize key aspects of the code.
2. Provide Context: Explain why the note is important and how it affects the code.

MARK Comments

MARK comments are used to organize your code into sections, making it easier to navigate and understand. They are especially useful in larger files.

// MARK: - Networking

func fetchDataFromServer() {
    // Networking code
}

// MARK: - UI Updates

func updateUI() {
    // UI update code
}

Best Practices for MARK Comments:

1. Use Consistent Formatting: Follow a consistent style for MARK comments.
2. Be Descriptive: Clearly describe the section being marked.