Generate UML class diagrams from swift code with this Command Line Interface (CLI) and Swift Package.

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Use one or more Swift files as input for a diagram to visualize class, struct, protocol, enum and extension types with their instance and static members as well as their inheritance and implementation relationships

Example Diagram

Table of Contents (click to expand) - [SwiftPlantUML](#swiftplantuml) - [Usage](#usage) - [Command Line](#command-line) - [Swift package](#swift-package) - [Xcode source editor extension](#xcode-source-editor-extension) - [Installation](#installation) - [Using Homebrew](#using-homebrew) - [Using Mint](#using-mint) - [Installing from source](#installing-from-source) - [Note: Working with Multiple Swift Versions](#note-working-with-multiple-swift-versions) - [Configuration](#configuration) - [Options](#options) - [Theming](#theming) - [Examples](#examples) - [Code Completion during Editing](#code-completion-during-editing) - [Large Diagrams](#large-diagrams) - [Generate UML documentation from a binary framework](#generate-uml-documentation-from-a-binary-framework) - [Planned improvements](#planned-improvements) - [Known limitations](#known-limitations) - [Logging](#logging) - [Manual page](#manual-page) - [Acknowledgements](#acknowledgements)


Command Line

Example to generate and render diagram, based on a single Swift file, in your browser:

swiftplantuml ./Tests/SwiftPlantUMLFrameworkTests/TestData/basics.txt

Run swiftplantuml in the directory containing the Swift files to be considered for diagram generation. Directories will be searched recursively.

$ swiftplantuml classdiagram --help
OVERVIEW: Generate PlantUML script and view it and diagram in browser

USAGE: swift-plant-uml classdiagram [--config <config>] [--exclude <exclude> ...] [--output <format>] [--sdk <sdk>] [--verbose] [<paths> ...]

  <paths>                 List of paths to the files or directories containing
                          swift sources

  --config <config>       Path to custom configuration filed (otherwise will
                          search for `.swiftplantuml.yml` in current directory)
  --exclude <exclude>     paths to ignore source files. Takes precedence over
  --output <format>       Defines output format. Options: browser,
                          browserImageOnly, consoleOnly
  --sdk <sdk>             MacOSX SDK path used to handle type inference
                          resolution, usually `$(xcrun --show-sdk-path -sdk
                          Decide if/how Swift extensions shall be considered for class diagram generation (default:
  --verbose               Verbose
  --version               Show the version.
  -h, --help              Show help information.

As classdiagram is the default subcommand you can omit it.

Note: unknown type in diagrams for variables declared with type inference (e.g. var hasBasket = false) unless you specify sdk argument

Type inference details (click to expand) In the following example the property `hasBasket` is of type `Bool` but the type is inferred and not explicitly declared. “`swift class Bicycle: Vehicle { var hasBasket = false } ”` SwiftPlantUML requires the macosx SDK in order to properly recognize the inferred type. If you have Xcode installed (which includes the macosx SDK) then use `–sdk $(xcrun –show-sdk-path -sdk macosx)`. | | No inferred type (*default*) | inferred type | |——————–|——————-|———————–| | Generated PlantUML | `~hasBasket` | `~hasBasket : Bool` | Command | `swiftplantuml classdiagram Tests/SwiftPlantUMLFrameworkTests/TestData/demo.txt` | `swiftplantuml classdiagram Tests/SwiftPlantUMLFrameworkTests/TestData/demo.txt –sdk $(xcrun –show-sdk-path -sdk macosx)` | |

Swift package

dependencies: [
    .package(url: "https://github.com/MarcoEidinger/SwiftPlantUML.git", .upToNextMajor(from: "0.5.0"))

This project has yet to reach a major version. Anything may change at anytime, and the public API should not be considered stable. However, I’ll try to reserve breaking changes for new minor versions. You might feel more comfortable pinning the version to .upToNextMinor or even to an .exact version.

API documentation

Xcode source editor extension

See MarcoEidinger/SwiftPlantUML-Xcode-Extension for more details


Using Homebrew

brew install swiftplantuml

previously you were able to use brew install MarcoEidinger/formulae/swiftplantuml (and you still can)

Using Mint

$ mint install MarcoEidinger/SwiftPlantUML

Installing from source

You can also build and install from source by cloning this project and running make install (Xcode 12 or later).

Manually Run the following commands to build and install manually:

$ git clone https://github.com/MarcoEidinger/SwiftPlantUML.git
$ cd SwiftPlantUML
$ make install

Note: Working with Multiple Swift Versions

SwiftPlantUML hooks into SourceKit and therefore needs a Swift toolschain.

You should always run SwiftPlantUML with the same toolchain you use to compile your code.

You may want to override SwiftPlantUML’s default Swift toolchain if you have multiple toolchains or Xcodes installed.

Here’s the order in which SwiftPlantUML determines which Swift toolchain to use:

  • xcrun -find swift
  • /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
  • /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
  • ~/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
  • ~/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain

sourcekitd.framework is expected to be found in the usr/lib/ subdirectory of the value passed in the paths above.

So if you encounter Fatal error: Loading sourcekitd.framework/Versions/A/sourcekitd failed then please check result of xcode-select -p to see if that directory subsequently contains a Swift toolschain. You can use sudo xcode-select -s <pathToYourXcodeInstallation> to rectify the situation, e.g.

sudo xcode-select -s /Applications/Xcode.app/Contents/Developer


Configure SwiftPlantUML by adding a .swiftplantuml.yml file from the directory you’ll run SwiftPlantUML from. Note: the same configuration options can be set programmatically with Configuration.


You can

  • include/exclude files (wildcards supported)
  • include/exclude elements by name (wildcards supported)
  • limit elements and members based on their access level, e.g. show only public types
  • hide extensions or merge extensions (with their known type)
Show Extensions (Default) Merge Extensions Hide Extensions
Show Extensions Merge Extensions Hide Extensions
Clutter but represents codebase accurately Reduced clutter. No loss of information No clutter but loss of information
  • hide nested types
  • hide member access level attribute
  • configure styles, use skin parameters and even include external files or themes
  • exclude inheritance relationships based on parent (wildcards supported), e.g. do not show inheritance to Codable


Default Amiga Reddress-darkblue Sketchy Outline Many More Available
default amiga reddress-darkblue sketchy-outline See here for more examples


Simple Example:

    - "Tests/**/*.swift" # paths to ignore for diagram. Takes precedence over `included`.
  - public
  - open
  - public
  - open
  showNestedTypes: false
  showExtensions: merged
theme: plain # see https://plantuml.com/theme
  title: |
    <u>Formatted</u> title example
    on <i>several</i> lines and using <font color=red>html</font>
skinparamCommands: # see https://plantuml.com/skinparam
- skinparam classBackgroundColor PaleGreen
- skinparam classArrowColor SeaGreen
- skinparam classBorderColor SpringGreen
- skinparam stereotypeCBackgroundColor YellowGreen
- skinparam stereotypeCBackgroundColor<< Foo >> DimGray
    label: "inherits from"
      lineStyle: dotted
      lineColor: DarkViolet
      textColor: DarkViolet
    - "Codable"

Rich example: here

Code Completion during Editing


To get code completion during editing use Visual Studio Code, the YAML extension created by Red Hat and the JSON schema for SwiftPlantUML.

In Visual Studio Code: Code -> Preferences -> Settings -> search for yaml

Screen Shot 2021-02-27 at 5 57 49 AM

Click on Edit in settings.json and add the respective entry:

"yaml.schemas": {"https://raw.githubusercontent.com/MarcoEidinger/SwiftPlantUML/main/Configuration/Schema/json-schema-swiftplantuml.json": "/.swiftplantuml.yml" }

Large Diagrams

Online tools like PlantText do not support large diagrams. If your diagram image is incompletely rendered (or not visible at all) by PlantText in the browser then

  • download PlantUML Java archive to your machine
  • use swiftplantuml to generate the script and
  • generate the actual image with plantuml locally

Here is the respective command (which assumes that plantuml.jar was downloaded in the current directory from which swifptlantuml runs)

swiftplantuml ./Sources/ --output consoleOnly > sources.txt | java -DPLANTUML_LIMIT_SIZE=8192 -jar plantuml.jar $1

This will result in the creation of sources.png file containing the class diagram up to the size limit.

PlantUML limits image width and height to 4096 with the option to override this limit (-DPLANTUML_LIMIT_SIZE) of which I made use in the command above.

In the table below you see the difference of class diagram output based on the same script. FYI: this script/diagram has 63 entities.

PlantText Output PlantUML Output (Default Size Limit) PlantUML Output (Custom Size Limit)
sources_planttext sources_plantumljar sources_plantumljar_increasedlimit

Generate UML documentation from a binary framework

You can use swifplantuml to parse the .swiftmodule file of a binary framework, for details and a concrete example please read my article Generate UML documentation from a binary framework (xcframework).

Planned improvements

  • being able to render associations between elements

Known limitations

See Large Diagrams


CLI will log only error messages per default.

To log messages with lower priority (warning, info, debug) use the --verbose option.

Note: using --output consoleOnly, to print the PlantUML script in the console, will log any messages into a log file. This has the advantage that you can pipe the PlantUML script into a file without problems. You can tail the log file with tail -f /tmp/swiftplantuml.log

Manual page

Installing swiftplantuml with Homebrew or from source (make install) will also install a man page which you can view with:

man swiftplantuml

manual page for swiftplantuml


This project was inspired by https://github.com/palaniraja/swiftuml and its various predecessors. Out of personal preference I chose to start a new project. I wanted to provide a tool for Swift developers written in Swift! This will hopefully allow me and potential contributors to work on planned improvements faster and more efficient.

Last but not least a big shoutout to the great developers of PlantUML and the people who operate the related online servers / tools available on http://plantuml.com/ and https://www.planttext.com/