Documentation is a crucial part of software development. It helps other developers (and your future self) understand the purpose, usage, and functionality of your code. Rust provides robust tools for creating and maintaining documentation directly within your codebase.
Key Concepts
- Doc Comments: Special comments that generate documentation.
- Markdown: A lightweight markup language used to format the documentation.
- Cargo: Rust's package manager and build system, which includes tools for generating and viewing documentation.
Doc Comments
Rust uses three types of comments:
- Line comments (
//) - Block comments (
/* */) - Doc comments (
///and//!)
Line Doc Comments
Line doc comments start with /// and are placed directly above the item they document.
/// Adds two numbers together.
///
/// # Examples
///
/// ```
/// let result = add(2, 3);
/// assert_eq!(result, 5);
/// ```
fn add(a: i32, b: i32) -> i32 {
a + b
}Block Doc Comments
Block doc comments start with //! and are typically used to document the enclosing item, such as a module or crate.
//! This module provides basic arithmetic operations.
/// Subtracts one number from another.
///
/// # Examples
///
/// ```
/// let result = subtract(5, 3);
/// assert_eq!(result, 2);
/// ```
fn subtract(a: i32, b: i32) -> i32 {
a - b
}Markdown
Rust doc comments support Markdown, allowing you to format text, create lists, add code blocks, and more.
Common Markdown Elements
- Headers: Use
#,##,###, etc. - Lists: Use
-,*, or1.,2., etc. - Code Blocks: Use triple backticks (```) for code blocks.
Example:
/// Multiplies two numbers.
///
/// # Examples
///
/// ```
/// let result = multiply(4, 5);
/// assert_eq!(result, 20);
/// ```
///
/// # Panics
///
/// This function will panic if the result overflows.
fn multiply(a: i32, b: i32) -> i32 {
a * b
}Generating Documentation
Rust's package manager, Cargo, can generate HTML documentation from your doc comments.
Generating Documentation
Run the following command in your project's root directory:
This command generates documentation for your project and its dependencies in the target/doc directory.
Viewing Documentation
To view the generated documentation in your web browser, use:
This command opens the documentation in your default web browser.
Practical Exercise
Exercise
- Create a new Rust project using Cargo.
- Write a simple module with a few functions.
- Add doc comments to each function, including examples and descriptions.
- Generate and view the documentation.
Solution
- Create a new project:
- Edit
src/lib.rs:
/// This module provides basic arithmetic operations.
pub mod arithmetic {
/// Adds two numbers together.
///
/// # Examples
///
/// ```
/// let result = arithmetic::add(2, 3);
/// assert_eq!(result, 5);
/// ```
pub fn add(a: i32, b: i32) -> i32 {
a + b
}
/// Subtracts one number from another.
///
/// # Examples
///
/// ```
/// let result = arithmetic::subtract(5, 3);
/// assert_eq!(result, 2);
/// ```
pub fn subtract(a: i32, b: i32) -> i32 {
a - b
}
}- Generate and view the documentation:
Conclusion
In this section, you learned how to document your Rust code using doc comments and Markdown. You also learned how to generate and view documentation using Cargo. Proper documentation is essential for maintaining and sharing your code, making it easier for others to understand and use your work. In the next topic, we will cover best practices to ensure your Rust code is clean, efficient, and maintainable.