Skill: Resources

Guide for the Resources module: localization and shared resources.

When to use this skill

• •Work with localized strings
• •Add new translations
• •Understand the localization system
• •Add support for a new language

Module Overview

The Resources module provides app-specific resources used across features:

• •Localization: Centralized strings with String.localized() extension
• •Bundle: Manual Bundle.module accessor for resources

Location: Shared/Resources/

Note: Shared modules are app-specific (not reusable across apps), unlike Libraries which are generic and reusable.

Supported Languages

The app uses .xcstrings format (Apple's modern localization format for iOS 16+).

Structure:

Shared/Resources/
├── Sources/
│   ├── Extensions/
│   │   ├── Bundle+Module.swift       # Bundle.module accessor
│   │   └── String+Localized.swift    # localized() extension
│   └── Resources/
│       └── Localizable.xcstrings
└── Tests/

Localization

All localized strings are centralized in the Resources module.

Location: Shared/Resources/Sources/Resources/Localizable.xcstrings

String Extension

The localized() extension converts string keys to localized values:

// Shared/Resources/Sources/Extensions/String+Localized.swift
public extension String {
    func localized() -> String {
        String(localized: LocalizationValue(self), bundle: .module)
    }

    func localized(_ arguments: CVarArg...) -> String {
        let localizedFormat = String(localized: LocalizationValue(self), bundle: .module)
        return String(format: localizedFormat, arguments: arguments)
    }
}

Expected Xcode Warnings

When building, Xcode may show these warnings:

Skipping extraction of localizable string with non-literal key

These warnings are expected and safe to ignore. They occur because Xcode's automatic string extraction cannot analyze dynamic keys like LocalizationValue(self). The localization system works correctly—these warnings only indicate that Xcode won't auto-extract keys from localized() calls.

Why this pattern? It allows type-safe, reusable localization without repeating bundle references. Translations are managed manually in .xcstrings files.

Usage in Views

Each View defines a private LocalizedStrings enum that uses localized():

import {AppName}Resources

struct MyView: View {
    var body: some View {
        Text(LocalizedStrings.title)
    }
}

// MARK: - LocalizedStrings

private enum LocalizedStrings {
    static var title: String { "myView.title".localized() }
    static var subtitle: String { "myView.subtitle".localized() }
    static func itemCount(_ count: Int) -> String {
        "myView.itemCount %lld".localized(count)
    }
}

Adding New Strings

1. •Add the key to Shared/Resources/Sources/Resources/Localizable.xcstrings
2. •Provide translations for all supported languages (en, es)
3. •Add the string to the View's private LocalizedStrings enum

String Key Naming Convention

Bundle.module

The Bundle+Module.swift file provides access to the module's resource bundle.

Why manual? Tuist's bundle accessor generation is disabled (disableBundleAccessors: true) to avoid generated code.

// Shared/Resources/Sources/Extensions/Bundle+Module.swift
import Foundation

private final class BundleFinder {}

extension Bundle {
    static let module = Bundle(for: BundleFinder.self)
}

Used by: String.localized() to access Localizable.xcstrings.

Note: Any module needing Bundle.module must include its own Bundle+Module.swift.

Project Configuration

The main app must declare supported languages in Project.swift via CFBundleLocalizations:

// Project.swift
let appInfoPlist: [String: Plist.Value] = [
    "CFBundleLocalizations": ["en", "es"],
    // ...
]

Important: iOS does not load localizations from embedded frameworks unless the main app declares supported languages in CFBundleLocalizations. Without this configuration, the app will always display the development language (English) regardless of device settings.

Adding a New Language

1. •Open Localizable.xcstrings in Xcode
2. •Click the "+" button to add a new language
3. •Translate all strings to the new language
4. •Update CFBundleLocalizations in Project.swift:
   swift

   "CFBundleLocalizations": ["en", "es", "NEW_LANG_CODE"],
   

5. •Regenerate the project: ./generate.sh

Checklist

Adding Localized Strings

• • Add key to Localizable.xcstrings with all translations
• • Add to View's private LocalizedStrings enum
• • Use localized() or localized(_:) for interpolation

Adding a New Language

• • Add language to Localizable.xcstrings in Xcode
• • Translate all existing strings
• • Add language code to CFBundleLocalizations in Project.swift
• • Regenerate project with ./generate.sh