How to streamline your strings localization with String Catalogs

During WWDC 2023, Apple unveiled String Catalogs with the goal to make your app localization easier and faster to handle. Prior to String Catalogs, as a developer, you had to manage two files: Strings files and Strings Dictionaries files. You usually used Strings files for simple and static strings while Stringsdict files are used for complex strings (like plural and contextual strings).

Starting from Xcode 15, String Catalogs allows us to manage all strings in one file and make sure all of the strings are synced and localized before shipping the app to the users. So no room to error any more.

Let’s see together how powerful is String Catalogs, open Xcode (15 or later) and create a new project.

Let’s localise the “Hello, world!” default string you get in the preview.

Select File\New\File from Template from the menu (or cmd+N).

From the list choose String Catalog, leave its name as Localizable and save it.

How to streamline your strings localization with String Catalogs

Once added to the project, select it from the Project navigator, you will notice it is empty.

Build the project (Product\Build from the menu) or cmd+B, and here we go, the “Hello, World!” string is now automatically added to the Localizable strings file. Magic, isn’t ?

The heavy lifting is now done by Xcode, you don’t have to manually add strings yourself, so you can focus on more important things in your app.

Let’s add a new button to the screen, change your code to the following:

var body: some View {
    VStack {
        Image(systemName: "globe")
            .imageScale(.large)
            .foregroundStyle(.tint)
        Text("Hello, world!")
        Button("Tap me") {
        }
    }
    .padding()
}

Same thing, build the project and notice how the string is automatically added to the Localizable strings file.

Multi-platform strings support

Now assume your app is multi-platform and you want to support macOS, a text like “Tap me” would be only relevant to touch screens, for mac apps, the text would be “Click me” instead.

To achieve this, right click on the string in the Localizable file and select “Vary by Device\Mac”.

Now edit the text for Mac as follows.

Change the run destination to Mac and run the project.

The change should automatically reflect on the SwiftUI preview as well but sometimes it is so slow to render and I find it faster to run the target on a simulator instead of waiting for the preview.

Let’s finish up by adding support for another language, click the “+” icon at the bottom of the Localizable file window and select French.

Once added, you will notice the text is automatically populated into the new language file with the percentage of the translation progress into the new language. In this case 0% means no string has been translated into French yet.