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The Swift code generator for your assets, storyboards, Localizable.strings, … — Get rid of all String-based APIs!

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SwiftGen

CircleCI CocoaPods Compatible Platform

SwiftGen is a tool to auto-generate Swift code for resources of your projects, to make them type-safe to use.

SwiftGen Logo Then generate code (enums, constants, etc) for:

There are multiple benefits in using this:

  • Avoid any typo you could have when using a String
  • Free auto-completion
  • Avoid the risk to use an non-existing asset name
  • All this will be ensured by the compiler.

Also, it's fully customizable thanks to Stencil templates, so even if it comes with predefined templates, you can make your own to generate whatever code fits your needs and your guidelines!

Installation

There are multiple possibilities to install SwiftGen on your machine or in your project, depending on your preferences and needs:

Download the ZIP for the latest release

We recommend that you unarchive the ZIP inside your project directory and commit its content to git. This way, all coworkers will use the same version of SwiftGen for this project.

If you unarchived the ZIP file in a folder e.g. called swiftgen at the root of your project directory, you can then invoke SwiftGen in your Script Build Phase using:

"$PROJECT_DIR"/swiftgen/bin/swiftgen …
Via CocoaPods

If you're using CocoaPods, you can simply add pod 'SwiftGen' to your Podfile.

This will download the SwiftGen binaries and dependencies in Pods/ during your next pod install execution.

Given that you can specify an exact version for SwiftGen in your Podfile, this allows you to ensure all coworkers will use the same version of SwiftGen for this project.

You can then invoke SwiftGen in your Script Build Phase using:

$PODS_ROOT/SwiftGen/bin/swiftgen …

Note: SwiftGen isn't really a pod, as it's not a library your code will depend on at runtime; so the installation via CocoaPods is just a trick that installs the SwiftGen binaries in the Pods/ folder, but you won't see any swift files in the Pods/SwiftGen group in your Xcode's Pods.xcodeproj. That's normal: the SwiftGen binary is still present in that folder in the Finder.

Via Homebrew (system-wide installation)

To install SwiftGen via Homebrew, simply use:

$ brew update
$ brew install swiftgen

This will install SwiftGen system-wide. The same version of SwiftGen will be used for all projects on that machine, and you should make sure all your coworkers have the same version of SwiftGen installed on their machine too.

You can then invoke swiftgen directly in your Script Build Phase (as it will be in your $PATH already):

swiftgen …

Note: SwiftGen needs Xcode 8.3 to build, so installing via Homebrew requires you to have Xcode 8.3 installed (which in turn requires macOS 10.12). If you use an earlier version of macOS, you'll have to use one of the other installation methods instead.

Compile from source (only recommended if you need features from master or want to test a PR)

This solution is when you want to build and install the latest version from master and have access to features which might not have been released yet.

  • If you have homebrew installed, you can use the following command to build and install the latest commit:
brew install swiftgen --HEAD
  • Alternatively, you can clone the repository and use rake cli:install to build the tool and install it from any branch, which could be useful to test SwiftGen in a fork or a Pull Request branch.

You can install to the default locations (no parameter) or to custom locations:

# Binary is installed in `./swiftgen/bin`, frameworks in `./swiftgen/lib` and templates in `./swiftgen/templates`
$ rake cli:install
# - OR -
# Binary will be installed in `~/swiftgen/bin`, frameworks in `~/swiftgen/fmk` and templates in `~/swiftgen/tpl`
$ rake cli:install[~/swiftgen/bin,~/swiftgen/fmk,~/swiftgen/tpl]

You can then invoke SwiftGen using the path to the binary where you installed it:

~/swiftgen/bin/swiftgen …

Or add the path to the bin folder to your $PATH and invoke swiftgen directly.

Usage

❗️ If you're migrating from SwiftGen 4.x to SwiftGen 5.x, don't forget to read the Migration Guide.

The tool is provided as a unique swiftgen binary command-line, with the following subcommands available to parse various resource types:

  • swiftgen colors [OPTIONS] FILE1 …
  • swiftgen fonts [OPTIONS] DIR1 …
  • swiftgen storyboards [OPTIONS] DIR1 …
  • swiftgen strings [OPTIONS] FILE1 …
  • swiftgen xcassets [OPTIONS] CATALOG1 …

Each subcommand has its own option and syntax, but some options are common to all:

  • --output FILE or -o FILE: set the file where to write the generated code. If omitted, the generated code will be printed on stdout.
  • --template NAME or -t NAME: define the Stencil template to use (by name, see here for more info) to generate the output.
  • --templatePath PATH or -p PATH: define the Stencil template to use, using a full path.
  • Note: you should specify one and only one template when invoking SwiftGen. You have to use either -t or -p but should not use both at the same time (it wouldn't make sense anyway and you'll get an error if you try)
  • Each command supports multiple input files (or directories where applicable).

There are also more subcommands not related to generate code but more oriented for help and configuration, namely:

  • The swiftgen templates subcommands helps you print, duplicate, find and manage templates (both bundled and custom)
  • The swiftgen config subcommands helps you manage configuration files (see below)
  • You can use --help on swiftgen or one of its subcommand to see the detailed usage.

Using a configuration file

Instead of having to invoke SwiftGen manually for each type or resource you want to generate code for, each time with the proper list of arguments, it's easier to use a configuration file.

Simply create a swiftgen.yml YAML file to list all the subcommands to invoke, and for each subcommand, the list of arguments to pass to it. For example:

strings:
  paths: Resources/Base.lproj/Localizable.strings
  templateName: structured-swift3
  output: Generated/strings.swift
xcassets:
  paths:
   - Resources/Images.xcassets
   - Resources/MoreImages.xcassets
  templateName: swift3
  output: Generated/assets-images.swift

Then you just have to invoke swiftgen config run, or even just swiftgen for short, and it will execute what's described in the configuration file

To learn more about the configuration file — its more detailed syntax and possiblities, how to pass custom parameters, using swiftgen config lint to validate it, how to use alternate config files, and other tips — see the dedicated documentation.

Choosing your template

SwiftGen is based on templates (it uses Stencil as its template engine). This means that you can choose the template that fits the Swift version you're using — and also the one that best fits your preferences — to adapt the generated code to your own conventions and Swift version.

Bundled templates vs. Custom ones

SwiftGen comes bundled with some templates for each of the subcommand (colors, fonts, storyboards, strings, xcassets), which will fit most needs. But you can also create your own templates if the bundled ones don't suit your coding conventions or needs. Simply either use the -t / --template option to specify the name of the template to use, or store them somewhere else (like in your project repository) and use -p / --templatePath to specify a full path.

💡 You can use the swiftgen templates list command to list all the available templates (both custom and bundled templates) for each subcommand, list the template content and dupliate them to create your own.

For more information about how to create your own templates, see the dedicated documentation.

Templates bundled with SwiftGen:

As explained above, you can use swiftgen templates list to list all templates bundled with SwiftGen. For most SwiftGen subcommands, we provide, among others:

  • A swift2 template, compatible with Swift 2
  • A swift3 template, compatible with Swift 3
  • A swift4 template, compatible with Swift 4
  • Other variants, like flat-swift2/3/4 and structured-swift2/3/4 templates for Strings, etc.

You can find the documentation for each bundled template here in the repo, with documentation organized as one folder per SwiftGen subcommand, then one MarkDown file per template.
Each MarkDown file documents the Swift Version it's aimed for, the use case for that template (in which cases you might favor that template over others), the available --param parameters to customize it on invocation, and some code examples.

Don't hesitate to make PRs to share your improvements suggestions on the bundled templates 😉

Additional documentation

Playground

The SwiftGen.playground available in this repository will allow you to play with the code that the tool typically generates, and see some examples of how you can take advantage of it.

This allows you to have a quick look at how typical code generated by SwiftGen looks like, and how you will then use the generated constants in your code.

Markdown files

There are also a lot of documentation in the form of Markdown files in this repository and the related StencilSwiftKit repo as well. Be sure to check the "Documentation" folder of each repository.

Wiki

You can also see in the wiki some additional documentation, about:

Tutorials

You can also find other help & tutorial material on the internet, like this classroom about Code Generation I gave at FrenchKit in Sept'17 — and its wiki detailing a step-by-step tutorial about installingn and using SwiftGen (and Sourcery too)

Asset Catalog

swiftgen xcassets -t swift3 /dir/to/search/for/imageset/assets

This will generate an enum Asset with one case per image set in your assets catalog, so that you can use them as constants.

Example of code generated by the bundled template 
enum Asset {
  enum Exotic {
    static let banana: AssetType = "Exotic/Banana"
    static let mango: AssetType = "Exotic/Mango"
  }
  static let `private`: AssetType = "private"
}

Usage Example

// You can create new images with the convenience constructor like this:
let bananaImage = UIImage(asset: Asset.Exotic.banana)  // iOS
let privateImage = NSImage(asset: Asset.private)  // macOS

// Or as an alternative, you can refer to enum instance and call .image on it:
let sameBananaImage = Asset.Exotic.banana.image
let samePrivateImage = Asset.private.image

Colors

swiftgen colors -t swift3 /path/to/colors-file.txt

This will generate a enum ColorName with one case per color listed in the text file passed as argument.

The input file is expected to be either:

  • a plain text file, with one line per color to register, each line being composed by the Name to give to the color, followed by ":", followed by the Hex representation of the color (like rrggbb or rrggbbaa, optionally prefixed by # or 0x). Whitespaces are ignored.
  • a JSON file, representing a dictionary of names -> values, each value being the hex representation of the color
  • a XML file, expected to be the same format as the Android colors.xml files, containing tags <color name="AColorName">AColorHexRepresentation</color>
  • a *.clr file used by Apple's Color Paletes.

For example you can use this command to generate colors from one of your system color lists:

swiftgen colors -swift3 ~/Library/Colors/MyColors.clr

Generated code will look the same as if you'd use text file.

Example of code generated by the bundled template

Given the following colors.txt file:

Cyan-Color       : 0xff66ccff
ArticleTitle     : #33fe66
ArticleBody      : 339666
ArticleFootnote  : ff66ccff
Translucent      : ffffffcc

The generated code will look like this:

struct ColorName {
  let rgbaValue: UInt32
  var color: Color { return Color(named: self) }

  /// <span style="display:block;width:3em;height:2em;border:1px solid black;background:#339666"></span>
  /// Alpha: 100% <br/> (0x339666ff)
  static let articleBody = ColorName(rgbaValue: 0x339666ff)
  /// <span style="display:block;width:3em;height:2em;border:1px solid black;background:#ff66cc"></span>
  /// Alpha: 100% <br/> (0xff66ccff)
  static let articleFootnote = ColorName(rgbaValue: 0xff66ccff)

  ...
}

Usage Example

// You can create colors with the convenience constructor like this:
let title = UIColor(named: .articleBody)  // iOS
let footnote = NSColor(named: .articleFootnote) // macOS

// Or as an alternative, you can refer to enum instance and call .color on it:
let sameTitle = ColorName.articleBody.color
let sameFootnote = ColorName.articleFootnote.color

This way, no need to enter the color red, green, blue, alpha values each time and create ugly constants in the global namespace for them.

Fonts

swiftgen fonts -t swift3 /path/to/font/dir

This will recursively go through the specified directory, finding any typeface files (TTF, OTF, …), defining a struct FontFamily for each family, and an enum nested under that family that will represent the font styles.

Example of code generated by the bundled template 
enum FontFamily {
  enum SFNSDisplay: String, FontConvertible {
    static let regular = FontConvertible(name: ".SFNSDisplay-Regular", family: ".SF NS Display", path: "SFNSDisplay-Regular.otf")
  }
  enum ZapfDingbats: String, FontConvertible {
    static let regular = FontConvertible(name: "ZapfDingbatsITC", family: "Zapf Dingbats", path: "ZapfDingbats.ttf")
  }
}

Usage

// You can create fonts with the convenience constructor like this:
let displayRegular = UIFont(font: FontFamily.SFNSDisplay.regular, size: 20.0) // iOS
let dingbats = NSFont(font: FontFamily.ZapfDingbats.regular, size: 20.0)  // macOS

// Or as an alternative, you can refer to enum instance and call .font on it:
let sameDisplayRegular = FontFamily.SFNSDisplay.regular.font(size: 20.0)
let sameDingbats = FontFamily.ZapfDingbats.regular.font(size: 20.0)

Storyboards

swiftgen storyboards -t swift3 /dir/to/search/for/storyboards

This will generate an enum for each of your NSStoryboard/UIStoryboard, with one case per storyboard scene.

Example of code generated by the bundled template

The generated code will look like this:

enum StoryboardScene {
  enum Dependency: StoryboardType {
    static let storyboardName = "Dependency"

    static let dependent = SceneType<UIViewController>(storyboard: Dependency.self, identifier: "Dependent")
  }
  enum Message: StoryboardType {
    static let storyboardName = "Message"

    static let messagesList = SceneType<UITableViewController>(storyboard: Message.self, identifier: "MessagesList")
  }
}

enum StoryboardSegue {
  enum Message: String, SegueType {
    case embed
    case nonCustom
  }
}

Usage Example

// You can instantiate scenes using the `instantiate` method:
let vc = StoryboardScene.Dependency.dependent.instantiate()

// You can perform segues using:
vc.perform(segue: StoryboardSegue.Message.embed)

// or match them (in prepareForSegue):
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
  switch StoryboardSegue.Message(rawValue: segue.identifier!)! {
  case .embed:
    // Prepare for your custom segue transition
  case .nonCustom:
    // Pass in information to the destination View Controller
  }
}

Strings

swiftgen strings -t structured-swift3 /path/to/Localizable.strings

This will generate a Swift enum L10n that will map all your Localizable.strings (or other tables) keys to an enum case. Additionaly, if it detects placeholders like %@,%d,%f, it will add associated values to that case. Note that all dots within the key are converted to dots in code.

Example of code generated by the structured bundled template

Given the following Localizable.strings file:

"alert_title" = "Title of the alert";
"alert_message" = "Some alert body there";
"apples.count" = "You have %d apples";
"bananas.owner" = "Those %d bananas belong to %@.";

Reminder: Don't forget to end each line in your *.strings files with a semicolon ;! Now that in Swift code we don't need semi-colons, it's easy to forget it's still required by the Localizable.strings file format 😉

The generated code will contain this:

enum L10n {
  /// Some alert body there
  static let alertMessage = L10n.tr("alert_message")
  /// Title of the alert
  static let alertTitle = L10n.tr("alert_title")

  enum Apples {
    /// You have %d apples
    static func count(_ p1: Int) -> String {
      return L10n.tr("apples.count", p1)
    }
  }

  enum Bananas {
    /// Those %d bananas belong to %@.
    static func owner(_ p1: Int, _ p2: String) -> String {
      return L10n.tr("bananas.owner", p1, p2)
    }
  }
}

Usage Example

Once the code has been generated by the script, you can use it this way in your Swift code:

// Simple strings
let message = L10n.alertMessage
let title = L10n.alertTitle

// with parameters, note that each argument needs to be of the correct type
let apples = L10n.Apples.count(3)
let bananas = L10n.Bananas.owner(5, "Olivier")

Flat Strings Support

SwiftGen also has a template to support flat strings files (i.e. no dot syntax). The advantage is that your keys won't be mangled in any way, the disadvantage is worse auto-completion.

Example of code generated by the flat bundled template 
enum L10n {
  /// Some alert body there
  case alertMessage
  /// Title of the alert
  case alertTitle
  /// You have %d apples
  case applesCount(Int)
  /// Those %d bananas belong to %@.
  case bananasOwner(Int, String)
}

Given the same Localizable.strings as above the usage will now be:

// Simple strings
let message = L10n.alertMessage
let title = L10n.alertTitle

// with parameters, note that each argument needs to be of the correct type
let apples = L10n.applesCount(3)
let bananas = L10n.bananasOwner(5, "Olivier")

License

This code and tool is under the MIT License. See the LICENSE file in this repository.

Attributions

This tool is powered by

It is currently mainly maintained by @AliSoftware and @djbe. But I couldn't thank enough all the other contributors to this tool along the different versions which helped make SwiftGen awesome! 🎉

If you want to contribute, don't hesitate to open an Pull Request, or even join the team!

Other Libraries / Tools

If you want to also get rid of String-based APIs not only for your ressources, but also for UITableViewCell, UICollectionViewCell and XIB-based views, you should take a look I my Mixin Reusable.

If you want to generate Swift code from your own Swift code (so meta!), like generate Equatable conformance to your types and a lot of other similar things, use Sourcery.

SwiftGen and Sourcery are complementary tools. In fact, Sourcery uses Stencil too, as well as SwiftGen's StencilSwiftKit so you can use the exact same syntax for your templates for both!

You can also follow me on twitter for news/updates about other projects I am creating, or read my blog.

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The Swift code generator for your assets, storyboards, Localizable.strings, … — Get rid of all String-based APIs!

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