Swift packages: Resources and localization

Adding Resources to a Package

• New with Xcode 12/Swift 5.3

• Adding resources to a package works with existing APIs

• Adding resources does not affect the OS version requirements of our package

• To add resoruces, we create an assets catalog, a.k.a. a folder with .xcassets suffix, the same way as an Xcode project.

• to access to the package resources, we need to pass a bundle parameter where the resource is needed, for example: Image("myPackageImage", bundle: .module)

Resource purpose

• Some resources (as seen in the image below) are automatically added in the package assets, for example:

• Some other resources, that are not places in an assets catalog (for development purposes for example), need to have an intent declared in the package manifest

• In order to exclude assets or folders to be embed in our package, add these resources in the excluded array of the target

• In order to include standalone assets (a.k.a. assets not in an asset catalog), we need to declare them in with the resources array of its target.

  • most resources should use the .process action, so that they are transformed as appropriate at build time, the exact processing that depends on the platform for which the package is built.

  • in case we would like to have a full folder available at runtime, while also preserving its structure as it is, we will use the .copy type instead

// swift-tools-version:5.3
import PackageDescription

let package = Package(name: "MyPackage",
    products: [
        ...
    ],
    targets: [
        .target(name: "MyLibrary",
            excludes: [
                "Internal Notes.txt", // excluding this file
                "Artwork Creation"], // excluding this folder content on build time
            resources: [
                .process("Logo.png"), // processed and available at runtime
                .copy("Game Data")] // copied and available at runtime exactly as it is
        )
    ]
)

Localizing Resources

• first we need to add a default localization in the package declaration

let package = Package(
    name: ...
    defaultLocalization: "en", // mandatory if our package supports localizations
    products: [
        ...
    ],
    targets: [
        ...
    ]
)

• it works like an Xcode project: we create the languages en.lproj folders at the root of our target and add a Localizable.strings file in each with the localizations

• like for assets, wherever our localizations are needed we need to specify the bundle, for example: Text("user_greeting", bundle: .module)

• no need to declare the .lproj in the package manifest

• localized resources within the assets catalog are also supported