Rationale

While localization in SwiftUI is pretty straightforward, things get tricky when working across multiple modules, especially with Swift packages. The built-in localization system tends to target the main app bundle, which isn’t ideal when your project includes modules or packages that need to handle their own localized resources.

👉 Start by reading my post on How to Localize Text in SwiftUI.

💻 Take a look at the #Localize package on GitHub.

Using the macro

Being able to reduce boilerplate is pretty nice, and it's really easy to do so by creating small and simple macros.

The #Localize macro is really easy to start using:

// Assign to a variable
let localizedString = #Localize("This is a localized string")

// Use directly within SwiftUI
Text(#Localize("This is a localized text"))

The macro will expand like so:

let localizedString = #Localize("This is a localized string")
{
    #if SWIFT_PACKAGE
    LocalizedStringResource("This is a localized string", bundle: .atURL(Bundle.module.bundleURL))
    #else
    LocalizedStringResource("This is a localized string")
    #endif
}()

Caveats

✅ If you are in the context of an app target, the above code should work just fine.

⚠️ If you are in the context of a Swift package, you have to do a couple things first.

1. Make sure that your Swift package has a default localization defined.
2. Create a String catalog file inside your Swift package Resources folder (or whichever folder you've defined to contain your resources).

Here is an example Package manifest:

let package = Package(
    name: "MyLibrary",
    defaultLocalization: "en", // Make sure to define a default localization here
    platforms: [.iOS(.v16)],
    products: [
        .library(name: "MyLibrary", targets: ["MyLibrary"]),
    ],
    dependencies: [
        .package(url: "https://github.com/Mackarous/Localize.git", from: "1.0.0")
    ],
    targets: [
        .target(name: "MyLibrary", dependencies: ["Localize"]),
        .testTarget(name: "MyLibraryTests", dependencies: ["MyLibrary"]),
    ]
)