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Sebastien Lato
Sebastien Lato

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SwiftUI Internationalization & Localization Architecture (Scale Without Breaking UI)

#swiftui #localization #i18n #architecture

Localization is not “adding strings”.

It is:

  • layout adaptation
  • plural logic
  • dynamic text lengths
  • RTL support
  • formatting rules
  • runtime language switching

Most apps break the moment they leave English.

This post shows how to design localization-safe SwiftUI architecture from day one.

🧠 The Core Principle

Text is data, not decoration.

If your UI assumes English length, it is already broken.

🧱 1. Typed Localization Keys

Never use raw strings:

Text("welcome_title")
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Use keys:

enum L10n {
    static let welcomeTitle = LocalizedStringKey("welcome_title")
}
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Now refactors are safe.

🌍 2. Dynamic Layout First

Avoid fixed widths.

Bad:

.frame(width: 120)
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Good:

.frame(maxWidth: .infinity)
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Test with:

  • German
  • Arabic
  • Japanese

If it survives German, it’s safe.

🔁 3. Pluralization Support

Use .stringsdict:

<key>items_count</key>
<dict>
  <key>NSStringLocalizedFormatKey</key>
  <string>%#@items@</string>
</dict>
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SwiftUI:

Text("items_count \(count)")
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Never build plurals manually.

🧭 4. RTL Readiness

Use:

  • leading / trailing
  • HStack instead of absolute offsets
  • layoutDirection environment

Avoid .left / .right.

🧠 5. Locale-Aware Formatting 

Text(date, format: .dateTime.month().day())
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Never format manually.

🧪 6. Localization Testing

Enable pseudo-languages:

  • Double-length
  • RTL

Xcode → Scheme → Application Language.

If it breaks, fix now — not after release.

❌ 7. Common Anti-Patterns

Avoid:

  • string concatenation
  • hardcoded dates
  • fixed frames
  • embedded grammar
  • layout assumptions

🧠 Mental Model 

Language
 → Layout
   → Format
     → UI
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🚀 Final Thoughts

Localization is architecture.

Do it early, or pay for it forever.

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