SwiftGen is a tool to auto-generate Swift code for resources of your projects, to make them type-safe to use.
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| Then generate constants 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!
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
- Go to the GitHub page for the latest release
- Download the
swiftgen-x.y.z.zipfile associated with that release - Extract the content of the zip archive in your project directory
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, simply add pod 'SwiftGen', '~> 6.0' to your Podfile.
Then execute pod install --repo-update (or pod update SwiftGen if you want to update an existing SwiftGen installation) to download and install the SwiftGen binaries and dependencies in Pods/SwiftGen/bin/swiftgen next to your project.
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 …Similarly, be sure to use
Pods/SwiftGen/bin/swiftgeninstead of justswiftgenwhere we mention commands withswiftgenin the rest of the documentation.
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 swiftgenThis 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.
Via Mint (system-wide installation)
❗️SwiftGen 6.0 or higher only.
To install SwiftGen via Mint, simply use:
$ brew install libxml2
$ mint install SwiftGen/SwiftGenCompile 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
homebrewinstalled, 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:installto build the tool and install it from any branch, which could be useful to test SwiftGen in a fork or a Pull Request branch.
Some Ruby tools are used in the build process, and the system Ruby works well if you are running a recent macOS. However, if you are using rbenv you can run rbenv install to make sure you have a matching version of Ruby installed.
Then install the Ruby Gems:
# Install bundle if it isn't installed
gem install bundle
# Install the Ruby gems from Gemfile
bundle installYou can now install to the default locations (no parameter) or to custom locations:
# Binary is installed in `./build/swiftgen/bin`, frameworks in `./build/swiftgen/lib` and templates in `./build/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 $PATH and invoke swiftgen directly.
❗️ If you're migrating from older SwiftGen versions, don't forget to read the Migration Guide.
SwiftGen is provided as a single command-line tool which uses a configuration file to run various actions (subcommands).
Each action described in the configuration file (strings, fonts, ib, …) typically corresponds to a type of input resources to parse (strings files, IB files, Font files, JSON files, …), allowing you to generate constants for each types of those input files.
To use SwiftGen, simply create a swiftgen.yml YAML file to list all the subcommands to invoke, and for each subcommand, the list of arguments to pass to it. For example:
strings:
inputs: Resources/Base.lproj
filter: .+\.strings$
outputs:
- templateName: structured-swift4
output: Generated/strings.swift
xcassets:
inputs:
- Resources/Images.xcassets
- Resources/MoreImages.xcassets
outputs:
- templateName: swift4
output: Generated/assets-images.swiftThen 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 possibilities, 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.
There are also additional subcommands you can invoke from the command line to manage and configure SwiftGen:
- The
swiftgen configsubcommand to help you with the configuration file, especiallyswiftgen config lintto validate that your Config file is valid and has no errors - The
swiftgen templatessubcommands helps you print, duplicate, find and manage templates (both bundled and custom)
Lastly, you can use --help on swiftgen or one of its subcommand to see the detailed usage.
Directly invoking a subcommand
While we highly recommend the use a configuration file for performance reasons (especially if you have multiple outputs, but also because it's more flexible), it's also possible to directly invoke the available subcommands to parse various resource types:
swiftgen colors [OPTIONS] DIRORFILE1 …swiftgen coredata [OPTIONS] DIRORFILE1 …swiftgen fonts [OPTIONS] DIRORFILE1 …swiftgen ib [OPTIONS] DIRORFILE1 …swiftgen json [OPTIONS] DIRORFILE1 …swiftgen plist [OPTIONS] DIRORFILE1 …swiftgen strings [OPTIONS] DIRORFILE1 …swiftgen xcassets [OPTIONS] DIRORFILE1 …swiftgen yaml [OPTIONS] DIRORFILE1 …
One rare cases where this might be useful — as opposed to using a config file — is if you are working on a custom template and want to quickly test the specific subcommand you're working on at each iteration/version of your custom template, until you're happy with it.
Each subcommand generally accepts the same options and syntax, and they mirror the options and parameters from the configuration file:
--output FILEor-o FILE: set the file where to write the generated code. If omitted, the generated code will be printed onstdout.--templateName NAMEor-n NAME: define the Stencil template to use (by name, see here for more info) to generate the output.--templatePath PATHor-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
-tor-pbut should not use both at the same time (it wouldn't make sense anyway and you'll get an error if you try) --filter REGEXor-f REGEX: the filter to apply to each input path. Filters are applied to actual (relative) paths, not just the filename. Each command has a default filter that you can override with this option.- Note: use
.+to match multiple characters (at least one), and don't forget to escape the dot (\.) if you want to match a literal dot like for an extension. Add$at the end to ensure the path ends with the extension you want. Regular expressions will be case sensitive by default, and not anchored to the start/end of a path. For example, use.+\.xib$to match files with a.xibextension. Use a tool such as RegExr to ensure you're using a valid regular expression. - Each command supports multiple input files (or directories where applicable).
- You can always use the
--helpflag to see what options a command accept, e.g.swiftgen xcassets --help.
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.
SwiftGen comes bundled with some templates for each of the subcommand (colors, coredata, fonts, ib, json, plist, strings, xcassets, yaml), 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 templateName output option to specify the name of the template to use, or store them somewhere else (like in your project repository) and use templatePath output option 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.
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
swift3template, compatible with Swift 3 - A
swift4template, compatible with Swift 4 - Other variants, like
flat-swift3/4andstructured-swift3/4templates 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 parameters to customize it on invocation (using the params: key in your config file), and some code examples.
Don't hesitate to make PRs to share your improvements suggestions on the bundled templates 😉
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.
There is a lot of documentation in the form of Markdown files in this repository, and in the related StencilSwiftKit repository as well.
Be sure to check the "Documentation" folder of each repository.
Especially, in addition to the previously mentioned Migration Guide and Configuration File documentation, the Documentation/ folder in the SwiftGen repository also includes:
- A
templatessubdirectory that details the documentation for each of the templates bundled with SwiftGen (when to use each template, what the output will look like, and custom parameters to adjust them, …) - A
SwiftGenKit Contextssubdirectory that details the structure of the "Stencil Contexts", i.e. the Dictionary/YAML representation resulting of parsing your input files. This documentation is useful for people wanting to write their own templates, so that they know the structure and various keys available when writing their template, to construct the wanted generated output accordingly. - Various articles to provide best practices & tips on how to better take advantage of SwiftGen in your projects:
- Integrate SwiftGen in your Xcode project — so it rebuilds the constants every time you build
- Configure SwiftLint to help your developers use constants generated by SwiftGen
- Create a custom template, and watch a folder to auto-regenerate an output every time you save the template you're working on
- …and more
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 installing and using SwiftGen (and Sourcery too)
xcassets:
inputs: /dir/to/search/for/imageset/assets
outputs:
templateName: swift4
output: Assets.swiftThis 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"
}// 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.imagecolors:
inputs: /path/to/colors-file.txt
outputs:
templateName: swift4
output: Colors.swiftThis 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
rrggbborrrggbbaa, optionally prefixed by#or0x) or the name of another color in the file. 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
*.clrfile used by Apple's Color Palettes.
For example you can use this command to generate colors from one of your system color lists:
colors:
inputs: ~/Library/Colors/MyColors.clr
outputs:
templateName: swift4
output: Colors.swiftGenerated code will look the same as if you'd use a 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)
...
}// 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.colorThis way, no need to enter the color red, green, blue, alpha values each time and create ugly constants in the global namespace for them.
coredata:
inputs: /path/to/model.xcdatamodeld
outputs:
templateName: swift4
output: CoreData.swiftThis will parse the specified core data model(s), generate a class for each entity in your model containing all the attributes, and a few extensions if needed for relationships and predefined fetch requests.
Example of code generated by the bundled template
internal class MainEntity: NSManagedObject {
internal class func entityName() -> String {
return "MainEntity"
}
internal class func entity(in managedObjectContext: NSManagedObjectContext) -> NSEntityDescription? {
return NSEntityDescription.entity(forEntityName: entityName(), in: managedObjectContext)
}
@nonobjc internal class func fetchRequest() -> NSFetchRequest<MainEntity> {
return NSFetchRequest<MainEntity>(entityName: entityName())
}
@NSManaged internal var attributedString: NSAttributedString?
@NSManaged internal var binaryData: Data?
@NSManaged internal var boolean: Bool
@NSManaged internal var date: Date?
@NSManaged internal var float: Float
@NSManaged internal var int64: Int64
@NSManaged internal var manyToMany: Set<SecondaryEntity>
}
// MARK: Relationship ManyToMany
extension MainEntity {
@objc(addManyToManyObject:)
@NSManaged public func addToManyToMany(_ value: SecondaryEntity)
@objc(removeManyToManyObject:)
@NSManaged public func removeFromManyToMany(_ value: SecondaryEntity)
@objc(addManyToMany:)
@NSManaged public func addToManyToMany(_ values: Set<SecondaryEntity>)
@objc(removeManyToMany:)
@NSManaged public func removeFromManyToMany(_ values: Set<SecondaryEntity>)
}// Fetch all the instances of MainEntity
let request = MainEntity.fetchRequest()
let mainItems = try myContext.execute(request)
// Type-safe relationships: `relatedItem` will be a `SecondaryEntity?` in this case
let relatedItem = myMainItem.manyToMany.firstfonts:
inputs: /path/to/font/dir
outputs:
templateName: swift4
output: Fonts.swiftThis 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")
}
}// 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)ib:
inputs: /dir/to/search/for/storyboards
outputs:
- templateName: scenes-swift4
output: Storyboard Scenes.swift
- templateName: segues-swift4
output: Storyboard Segues.swiftThis will generate an enum for each of your NSStoryboard/UIStoryboard, with respectively one case per storyboard scene or segue.
Example of code generated by the bundled template
The generated code will look like this:
// output from the scenes template
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")
}
}
// output from the segues template
enum StoryboardSegue {
enum Message: String, SegueType {
case customBack = "CustomBack"
case embed = "Embed"
case nonCustom = "NonCustom"
case showNavCtrl = "Show-NavCtrl"
}
}// 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(segue) {
case .embed?:
// Prepare for your custom segue transition, passing information to the destionation VC
case .customBack?:
// Prepare for your custom segue transition, passing information to the destionation VC
default:
// Other segues from other scenes, not handled by this VC
break
}
}json:
inputs: /path/to/json/dir-or-file
outputs:
templateName: runtime-swift4
output: JSON.swift
yaml:
inputs: /path/to/yaml/dir-or-file
outputs:
templateName: inline-swift4
output: YAML.swiftThis will parse the given file, or when given a directory, recursively search for JSON and YAML files. It will define an enum for each file (and documents in a file where needed), and type-safe constants for the content of the file.
Unlike other subcommands, this parser is intended to allow you to use more custom inputs (as the formats are quite open to your needs) to generate your code. This means that for these subcommands (and the plist one), you'll probably be more likely to use custom templates to generate code properly adapted/tuned to your inputs, rather than using the bundled templates. To read more about writing your own custom templates, see see the dedicated documentation.
Example of code generated by the bundled template
internal enum JSONFiles {
internal enum Info {
private static let _document = JSONDocument(path: "info.json")
internal static let key1: String = _document["key1"]
internal static let key2: String = _document["key2"]
internal static let key3: [String: Any] = _document["key3"]
}
internal enum Sequence {
internal static let items: [Int] = objectFromJSON(at: "sequence.json")
}
}// This will be an dictionary
let foo = JSONFiles.Info.key3
// This will be an [Int]
let bar = JSONFiles.Sequence.itemsplist:
inputs: /path/to/plist/dir-or-file
outputs:
templateName: runtime-swift4
output: Plist.swiftThis will parse the given file, or when given a directory, recursively search for Plist files. It will define an enum for each file (and documents in a file where needed), and type-safe constants for the content of the file.
Unlike other subcommands, this parser is intended to allow you to use more custom inputs (as the format is quite open to your needs) to generate your code. This means that for this subcommand (and the json and yaml ones), you'll probably be more likely to use custom templates to generate code properly adapted/tuned to your inputs, rather than using the bundled templates. To read more about writing your own custom templates, see see the dedicated documentation.
Example of code generated by the bundled template
internal enum PlistFiles {
internal enum Test {
internal static let items: [String] = arrayFromPlist(at: "array.plist")
}
internal enum Stuff {
private static let _document = PlistDocument(path: "dictionary.plist")
internal static let key1: Int = _document["key1"]
internal static let key2: [String: Any] = _document["key2"]
}
}// This will be an array
let foo = PlistFiles.Test.items
// This will be an Int
let bar = PlistFiles.Stuff.key1strings:
inputs: /path/to/Localizable.strings
outputs:
templateName: structured-swift4
output: Strings.swiftThis will generate a Swift enum L10n that will map all your Localizable.strings (or other tables) keys to a static let constant. And if it detects placeholders like %@,%d,%f, it will generate a static func with the proper argument types instead, to provide type-safe formatting. 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
*.stringsfiles with a semicolon;! Now that in Swift code we don't need semi-colons, it's easy to forget it's still required by theLocalizable.stringsfile 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)
}
}
}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")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")This code and tool is under the MIT Licence. See the LICENCE file in this repository.
This tool is powered by
- Stencil and few other libs by Kyle Fuller
- SwiftGenKit and StencilSwiftKit, our internal frameworks at SwiftGen
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 a Pull Request, or even join the team!
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 at 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.