Swift
Does Swift have documentation generation support
Swift, Apple’s powerful and intuitive programming language, has rapidly become a favorite for developing iOS, macOS, watchOS, and tvOS applications. As projects grow in size and complexity, clear and comprehensive documentation becomes increasingly crucial for maintainability, collaboration, and onboarding new team members. One common question that arises is: Does Swift have documentation generation support? The answer is a resounding yes, but it involves understanding the tools and techniques available within the Swift ecosystem. Creating high-quality documentation is essential for any software project, and knowing how to leverage Swift’s capabilities in this area can significantly improve your development workflow and the usability of your code. Let’s explore the various methods and tools available to generate documentation for your Swift projects, ensuring your code is not only functional but also easily understandable by others (and your future self!). This article will delve into the specifics of using Swift’s built-in features and third-party tools to create comprehensive and professional documentation.
Understanding Swift’s Documentation Markup
Swift provides a built-in mechanism for documenting your code directly within the source files using markup syntax. This markup allows developers to embed documentation comments that can then be extracted and formatted into readable documentation. This approach promotes “documentation as code,” ensuring that your documentation stays closely synchronized with the code itself. Essentially, you are embedding instructions for documentation generation directly into your code, ensuring clarity and up-to-date accuracy.
The primary way to add documentation in Swift is through special comments that begin with three forward slashes (///) for single-line comments or a combination of / and / for multi-line comments. These comments can then include specific keywords and formatting to provide detailed information about your functions, classes, structs, and other code elements. For example, you can use keywords like - Parameter:, - Returns:, and - Throws: to document function parameters, return values, and potential errors, respectively. The syntax is heavily influenced by the Doxygen standard, which means tools that can parse Doxygen-style comments are generally compatible with Swift’s documentation markup. The use of this markup is a core element of good Swift development practices, improving code readability and maintainability. Learn more about best practices here.
Using this markup system provides several advantages, including ease of use and integration directly within your code. However, to fully leverage this, you need a tool to parse these comments and generate the actual documentation. Fortunately, there are several options available, both from Apple and from the broader open-source community.
Generating Documentation with Jazzy
Jazzy is a popular open-source command-line tool for generating documentation for Swift and Objective-C projects. Developed by Realm, Jazzy is designed to create beautiful and easily navigable documentation in HTML format. It parses your Swift code, extracts the documentation comments, and generates a static website that can be easily hosted and shared. Jazzy supports various customization options, allowing you to tailor the look and feel of your documentation to match your project’s branding.
To use Jazzy, you typically install it using RubyGems (gem install jazzy) and then run it from your project’s root directory. Jazzy automatically detects your Swift files and generates the documentation based on the comments you’ve included. You can configure Jazzy using a .jazzy.yaml file to specify options such as the output directory, the project name, and any additional documentation files you want to include. Jazzy also supports themes, allowing you to choose from a variety of pre-built templates or create your own custom theme. This flexibility makes Jazzy a powerful tool for creating professional-looking documentation that meets your specific needs. According to a Stack Overflow survey, Jazzy is one of the most popular documentation generation tools for Swift. Source: Stack Overflow Blog.
One of the key benefits of Jazzy is its ability to link directly to your source code from the generated documentation. This makes it easy for users to navigate from the documentation to the relevant code sections, enhancing their understanding of your project. It also supports Markdown syntax within your documentation comments, allowing you to add rich formatting, including headings, lists, and links. This ensures that your documentation is not only informative but also visually appealing and easy to read.
Using Xcode’s Built-in Documentation Support
Xcode, Apple’s integrated development environment (IDE), offers built-in support for viewing and interacting with documentation. While Xcode doesn’t directly generate a standalone documentation website like Jazzy, it provides a powerful documentation viewer that allows you to quickly access information about Swift’s standard library, frameworks, and your own custom code. By properly documenting your code using Swift’s markup syntax, you can take full advantage of Xcode’s documentation features.
Within Xcode, you can access documentation by option-clicking on any code element, which will display a pop-up window with the documentation for that element. You can also use the “Help” menu to search for specific symbols or browse the documentation for various frameworks. Xcode’s documentation viewer supports rich text formatting, code samples, and links to related topics, making it a valuable resource for developers. Furthermore, Xcode can automatically generate documentation snippets when you start typing a function or method signature. This feature encourages developers to document their code as they write it, ensuring that the documentation stays up-to-date. Xcode’s built-in support is seamlessly integrated into the development workflow, making it easy for developers to access and contribute to documentation. It also supports quick help, which allows you to quickly view documentation for any symbol simply by highlighting it and pressing Option-Click.
The ability to quickly access documentation within Xcode can significantly improve your productivity and reduce the time spent searching for information. However, it’s important to note that Xcode’s documentation is primarily intended for use within the IDE. If you need to generate a standalone documentation website for distribution, you’ll need to use a tool like Jazzy or SwiftDoc. Despite this limitation, Xcode’s built-in documentation support is an essential tool for any Swift developer.
SwiftDoc and Other Alternatives
While Jazzy is the most popular tool for Swift documentation generation, there are other alternatives available that may be better suited for specific projects or workflows. One notable alternative is SwiftDoc, which is another open-source tool designed to generate API documentation from Swift code. SwiftDoc aims to provide a simpler and more lightweight alternative to Jazzy, with a focus on generating clean and concise documentation.
SwiftDoc typically involves installing the tool via Homebrew or similar package manager and then running it against your Swift project. It parses the code and generates HTML documentation based on the documentation comments. While SwiftDoc might not have all the advanced features and customization options of Jazzy, it can be a good choice for smaller projects or when you need a quick and easy way to generate documentation. Furthermore, some developers opt to create custom documentation generation scripts using tools like SourceKitten, which provides programmatic access to Swift’s compiler information. This approach allows for maximum flexibility and control over the documentation generation process, but it requires more effort and expertise. According to GitHub, SourceKitten has over 3,000 stars, demonstrating its popularity in the Swift community. Source: SourceKitten GitHub.
Ultimately, the choice of documentation generation tool depends on your specific needs and preferences. Consider factors such as the size and complexity of your project, the level of customization required, and your familiarity with the different tools available. Experimenting with different options can help you find the tool that best fits your workflow and allows you to create high-quality documentation efficiently. Remember to consistently update your documentation as your code evolves to ensure that it remains accurate and helpful.
- Key takeaway 1: Swift supports documentation generation through markup syntax in comments.
- Key takeaway 2: Jazzy is a popular tool for creating beautiful documentation websites.
- Key takeaway 3: Xcode provides built-in documentation support within the IDE.
- Step 1: Document your code using Swift’s markup syntax.
- Step 2: Choose a documentation generation tool (e.g., Jazzy, SwiftDoc).
- Step 3: Configure the tool and generate the documentation.
- Step 4: Review and refine the documentation.
- Step 5: Host and share the documentation with your team or users.
- **Q: What is the best way to document Swift code?**
- A: The best way is to use Swift's markup syntax within your code comments. This allows you to embed documentation directly in your code, making it easier to keep up-to-date.
- **Q: Is Jazzy the only tool for generating Swift documentation?**
- A: No, there are other tools like SwiftDoc, and you can even create custom scripts using SourceKitten. However, Jazzy is the most popular and feature-rich option.
- **Q: How can I view documentation in Xcode?**
- A: You can view documentation by option-clicking on any code element or by using the "Help" menu to search for symbols.
- **Q: What is the purpose of documentation generation?**
- A: Documentation generation helps create readable and understandable documentation from code comments. This makes it easier for developers to understand, maintain, and collaborate on projects. Clear documentation also simplifies onboarding new team members and enhances the usability of your code.
Question & Answer :
Many languages support documentation comments to allow a generator (like javadoc or doxygen) to generate code documentation by parsing that same code.
Does Swift have any type documentation comment feature like this?
Documentation comments are supported natively in Xcode, producing smartly rendered documentation in Quick Help (both in the popover when ⌥-clicking symbols, and in the Quick Help Inspector ⌥⌘2).
Symbol documentation comments are now based on the same Markdown syntax used by rich playground comments, so a lot of what you can do in playgrounds can now be used directly in source code documentation.
For full details of the syntax, see Markup Formatting Reference. Note that there are some discrepancies between the syntax for rich playground comments & symbol documentation; these are pointed out in the document (e.g. block quotes can only be used in playgrounds).
Below is an example and a list of the syntax elements that currently work for symbol documentation comments.
Updates
Xcode 7 beta 4 ~ Added “- Throws: ...” as a top-level list item which appears alongside parameters and return descriptions in Quick Help.
Xcode 7 beta 1 ~ Some significant changes to syntax with Swift 2 - documentation comments now based on Markdown (same as playgrounds).
Xcode 6.3 (6D570) ~ Indented text is now formatted as code blocks, with subsequent indentations being nested. It doesn’t appear to be possible to leave a blank line in such a code block - trying to do so results in the text being tacked onto the end of the last line with any characters in it.
Xcode 6.3 beta ~ Inline code can now be added to documentation comments using backticks.
Example for Swift 2
/// Text like this appears in "Description". /// /// Leave a blank line to separate further text into paragraphs. /// /// You can use bulleted lists (use `-`, `+` or `*`): /// /// - Text can be _emphasised_ /// - Or **strong** /// /// Or numbered lists: /// /// 7. The numbers you use make no difference /// 0. The list will still be ordered, starting from 1 /// 5. But be sensible and just use 1, 2, 3 etc… /// /// --- /// /// More Stuff /// ========== /// /// Code /// ---- /// /// Use backticks for inline `code()`. Indentations of 4 spaces or more will create a code block, handy for example usage: /// /// // Create an integer, and do nothing with it /// let myInt = 42 /// doNothing(myInt) /// /// // Also notice that code blocks scroll horizontally instead of wrapping. /// /// Links & Images /// -------------- /// /// Include [links](https://en.wikipedia.org/wiki/Hyperlink), and even images: /// ///  /// /// - note: That "Note:" is written in bold. /// - requires: A basic understanding of Markdown. /// - seealso: `Error`, for a description of the errors that can be thrown. /// /// - parameters: /// - int: A pointless `Int` parameter. /// - bool: This `Bool` isn't used, but its default value is `false` anyway… /// - throws: A `BadLuck` error, if you're unlucky. /// - returns: Nothing useful. func doNothing(int: Int, bool: Bool = false) throws -> String { if unlucky { throw Error.BadLuck } return "Totally contrived." }
Syntax for Swift 2 (based on Markdown)
Comment Style
Both /// (inline) and /** */ (block) style comments are supported for producing documentation comments. While I personally prefer the visual style of /** */ comments, Xcode’s automatic indentation can ruin formatting for this comment style when copying/pasting as it removes leading whitespace. For example:
/** See sample usage: let x = method(blah) */
When pasting, the code block indentation is removed and it is no longer rendered as code:
/** See sample usage: let x = method(blah) */
For this reason, I generally use ///, and will use it for the rest of the examples in this answer.
Block Elements
Heading:
/// # My Heading
or
/// My Heading /// ==========
Subheading:
/// ## My Subheading
or
/// My Subheading /// -------------
Horizontal rule:
/// ---
Unordered (bulleted) lists:
/// - An item /// - Another item
You can also use + or * for unordered lists, it just has to be consistent.
Ordered (numbered) lists:
/// 1. Item 1 /// 2. Item 2 /// 3. Item 3
Code blocks:
/// for item in array { /// print(item) /// }
An indentation of at least four spaces is required.
Inline Elements
Emphasis (italics):
/// Add like *this*, or like _this_.
Strong (bold):
/// You can **really** make text __strong__.
Note that you cannot mix asterisks (*) and underscores (_) on the same element.
Inline code:
/// Call `exampleMethod(_:)` to demonstrate inline code.
Links:
/// [Link Text](https://en.wikipedia.org/wiki/Hyperlink)
Images:
/// 
The URL can be either a web URL (using “http://”) or an absolute file path URL (I can’t seem to get relative file paths to work).
The URLs for links and images can also be separated from the inline element in order to keep all URLs in one, manageable place:
/// A [link][1] an an ![image][2] /// /// ... /// /// [1]: http://www.example.com /// [2]: http://www.example.com/image.jpg
Keywords
In addition to the Markdown formatting, Xcode recognises other markup keywords to display prominently in Quick Help. These markup keywords mostly take the format - <keyword>: (the exception is parameter, which also includes the parameter name before the colon), where the keyword itself can be written with any combination of uppercase/lowercase characters.
Symbol Section keywords
The following keywords are displayed as prominent sections in the help viewer, below the “Description” section, and above the “Declared In” section. When included, their order is fixed as displayed below even though you can include them in whatever order you like in your comments.
See the fully documented list of section keywords and their intended uses in the Symbol Section Commands section of the Markup Formatting Reference.
/// - parameters: /// - <#parameter name#>: /// - <#parameter name#>: /// - throws: /// - returns:
Alternatively, you can write each parameter this way:
/// - parameter <#parameter name#>:
Symbol Description Field keywords
The following list of keywords are displayed as bold headings in the body of the “Description” section of the help viewer. They will appear in whatever order you write them in, as with the rest of the “Description” section.
Full list paraphrased from this excellent blog article by Erica Sadun. Also see the fully documented list of keywords and their intended uses in the Symbol Description Field Commands section of the Markup Formatting Reference.
Attributions:
/// - author: /// - authors: /// - copyright: /// - date:
Availability:
/// - since: /// - version:
Admonitions:
/// - attention: /// - important: /// - note: /// - remark: /// - warning:
Development State:
/// - bug: /// - todo: /// - experiment:
Implementation Qualities:
/// - complexity:
Functional Semantics:
/// - precondition: /// - postcondition: /// - requires: /// - invariant:
Cross Reference:
/// - seealso:
Exporting Documentation
HTML documentation (designed to mimic Apple’s own documentation) can be generated from inline documentation using Jazzy, an open-source command-line utility.
$ [sudo] gem install jazzy $ jazzy Running xcodebuild Parsing ... building site jam out ♪♫ to your fresh new docs in `docs`
Console example taken from this NSHipster article
