SwiftGen

This is a suite of tools written in Swift to auto-generate Swift code for various assets of your project:

• enums for your Assets Catalogs
• enums for your UIStoryboard and their Scenes
• enums for your UIColors.
• enums for your Localizable.strings strings.

Installation

Note: The tools are written in Swift 2.0 and need to be compiled with the latest Xcode 7.
The Rakefile will automatically find the copy of Xcode 7.x installed on your Mac (using mdfind) and use it to compile the tools.

Build and install the tools from source

Clone the repository and use rake to build the tool.

# will build the tools locally in `./bin`
$ rake all
# will install them in `/usr/local/bin`
$ rake install[/usr/local,/bin]

Via Homebrew

You can also install SwiftGen via Homebrew:

$ brew install swiftgen

Using the binaries & play with the Playground

• Once the tool has been generated, simply invoke them with the necessary arguments from the command line (see doc of each tool below). Invoking them without any argument will print a very basic "usage" help.
• Each tool generates the code to stdout, so you'll probably use a shell redirection to write that to a file (e.g. swiftgen-assets /path/to/Images.xcassets >Assets.swift)
• The SwiftGen.playground available in this repository will allow you to play with the code that the tools typically generates, and see some examples of how you can take advantage of it.

Note: The playground is in the Xcode 7 format, and uses its new concept of "Playground pages" to regroup multiple playground pages in a single Playground.

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Assets Catalogs

swiftgen-assets /dir/to/search/for/imageset/assets

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

Generated code

The generated code will look like this:

extension UIImage {
    enum Asset : String {
        case GreenApple = "Green-Apple"
        case RedApple = "Red-Apple"
        case Banana = "Banana"
        case BigPear = "Big_Pear"
        case StopButtonEnabled = "stop.button.enabled"
        
        var image: UIImage {
            return UIImage(named: self.rawValue)!
        }
    }
    
    convenience init(asset: Asset) {
        self.init(named: asset.rawValue)!
    }
}

Usage Example

let image1 = UIImage.Asset.Apple.image
let image2 = UIImage(asset: .Banana)

This way, no need to enter the "Banana" string in your code and risk any typo.

Benefits & Limitations

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.

Note that this script only generate extensions and code compatible with UIKit and UIImage. It would be nice to have an option to generate OSX code in the future.

UIStoryboard

swiftgen-storyboard /dir/to/search/for/storyboards

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

Generated code

The generated code will look like this:

protocol StoryboardScene : RawRepresentable {
    static var storyboardName : String { get }
    static func storyboard() -> UIStoryboard
    static func initialViewController() -> UIViewController
    func viewController() -> UIViewController
    static func viewController(identifier: Self) -> UIViewController
}

extension StoryboardScene where Self.RawValue == String {
    /* Implementation details */
}

extension UIStoryboard {
    struct Scene {
        enum Wizard : String, StoryboardScene {
            static let storyboardName = "Wizard"

            case CreateAccount = "CreateAccount"
            static func createAccountViewController() -> CreateAccViewController {
                return Wizard.CreateAccount.viewController() as! CreateAccViewController
            }

            case ValidatePassword = "Validate_Password"
            static func validatePasswordViewController() -> UIViewController {
                return Wizard.ValidatePassword.viewController()
            }
        }
        enum Message : String, StoryboardScene {
            static let storyboardName = "Message"

            case Composer = "Composer"
            static func composerViewController() -> UIViewController {
                return Message.Composer.viewController()
            }

            case URLChooser = "URLChooser"
            static func urlChooserViewController() -> XXPickerViewController {
                return Message.URLChooser.viewController() as! XXPickerViewController
            }
        }
    }

    struct Segue {
        enum Message : String {
            case Custom = "Custom"
            case Back = "Back"
            case NonCustom = "NonCustom"
        }
    }
}

Usage Example

// Initial VC
let initialVC = UIStoryboard.Scene.Wizard.initialViewController()
// Generic ViewController constructor, returns a UIViewController instance
let validateVC = UIStoryboard.Scene.Wizard.ValidatePassword.viewController()
// Dedicated type var that returns the right type of VC (CreateAccViewController here)
let createVC = UIStoryboard.Scene.Wizard.createAccountViewController()

override func prepareForSegue(_ segue: UIStoryboardSegue, sender sender: AnyObject?) {
  switch UIStoryboard.Segue.Message(rawValue: segue.identifier)! {
  case .Custom:
    // Prepare for your custom segue transition
  case .Back:
    // Prepare for your custom segue transition
  case .NonCustom:
    // Prepare for your custom segue transition
  }
}

UIColor

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

This tool will generate a enum Name in an extension of UIColor, with one case per color listed in the text file passed as argument.

The text file is expected to have 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.

Generated code

Given the following colors.txt file:

Cyan         : 0xff66ccff
ArticleTitle : #33fe66
ArticleBody  : 339666
Translucent  : ffffffcc

The generated code will look like this:

extension UIColor {
    /* Private Implementation details */
    ...
}

extension UIColor {
    enum Name : UInt32 {
        case Translucent = 0xffffffcc
        case ArticleBody = 0x339666ff
        case Cyan = 0xff66ccff
        case ArticleTitle = 0x33fe66ff
    }

    convenience init(named name: Name) {
        self.init(rgbaValue: name.rawValue)
    }
}

Usage Example

UIColor(named: .ArticleTitle)
UIColor(named: .ArticleBody)
UIColor(named: .Translucent)

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.

Localizable.strings

swiftgen-l10n /path/to/Localizable.strings

This tool generate a Swift enum L10n that will map all your Localizable.strings keys to an enum case. Additionaly, if it detects placeholders like %@,%d,%f, it will add associated values to that case.

Generated code

Given the following Localizable.strings file:

"alert_title" = "Title of the alert";
"alert_message" = "Some alert body there";
"greetings" = "Hello, my name is %@ and I'm %d";
"apples.count" = "You have %d apples";
"bananas.owner" = "Those %d bananas belong to %@.";

The generated code will contain this:

enum L10n {
	case AlertTitle
	case AlertMessage
	case Greetings(String, Int)
	case ApplesCount(Int)
	case BananasOwner(Int, String)
}

extension L10n : CustomStringConvertible {
	var description : String { return self.string }

	var string : String {
		/* Implementation Details */
	}
	...
}

func tr(key: L10n) -> String {
	return key.string
}

Usage Example

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

let title = L10n.AlertTitle.string
// -> "Title of the Alert"

// Alternative syntax, shorter
let msg = tr(.AlertMessage)
// -> "Body of the Alert"

// Strings with parameters
let nbApples = tr(.ApplesCount(5))
// -> "You have 5 apples"

// More parameters of various types!
let ban = tr(.BananasOwner(2, "John"))
// -> "Those 2 bananas belong to John."

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Licence

This code is under the MIT Licence.

Any ideas and contributions welcome!