Localization

DWallet features multi-language support built using slang - a type-safe i18n solution for Flutter.

Supported Languages

The app currently supports multiple languages with the infrastructure to easily add more.

How Localization Works

DWallet uses the slang package for type-safe translations:

1. Define translations in JSON/YAML files
2. Run code generation
3. Use generated classes for type-safe access

Directory Structure

lib/
├── i18n/                      # Translation files
│   ├── strings.i18n.json      # Base language (English)
│   ├── strings_es.i18n.json   # Spanish
│   └── strings_fr.i18n.json   # French
└── main.dart

Adding a New Language

1. Create Translation File

Create a new file in lib/i18n/:

lib/i18n/strings_ja.i18n.json

{
  "appName": "DWallet",
  "welcome": "ようこそ",
  "settings": {
    "title": "設定",
    "appearance": "外観",
    "language": "言語"
  },
  "wallet": {
    "title": "ウォレット",
    "balance": "残高",
    "addNew": "新規追加"
  }
}

2. Run Code Generation

flutter pub run slang

This generates type-safe translation classes.

3. Register the Locale

In main.dart, ensure the locale is supported:

ShadApp.router(
  localizationsDelegates: const [
    ...AppLocaleUtils.localizationsDelegates,
  ],
  supportedLocales: AppLocaleUtils.supportedLocales,
  // ...
)

Using Translations

In Widgets

import '../../i18n/strings.g.dart';

class HomeView extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final t = Translations.of(context);

    return Scaffold(
      appBar: AppBar(
        title: Text(t.wallet.title),
      ),
      body: Text(t.welcome),
    );
  }
}

With Riverpod

final localeProvider = StateProvider<AppLocale>((ref) {
  return AppLocale.en; // Default
});

// Change locale
ref.read(localeProvider.notifier).state = AppLocale.ja;

Translation Keys Structure

Organize translations hierarchically:

{
  "common": {
    "save": "Save",
    "cancel": "Cancel",
    "delete": "Delete",
    "confirm": "Are you sure?"
  },
  "home": {
    "title": "Home",
    "totalBalance": "Total Balance",
    "income": "Income",
    "expense": "Expense"
  },
  "transaction": {
    "add": "Add Transaction",
    "income": "Income",
    "expense": "Expense",
    "category": "Category",
    "amount": "Amount",
    "note": "Note"
  },
  "wallet": {
    "title": "Wallets",
    "add": "Add Wallet",
    "types": {
      "cash": "Cash",
      "bank": "Bank",
      "mobileMoney": "Mobile Money",
      "other": "Other"
    }
  },
  "settings": {
    "title": "Settings",
    "appearance": "Appearance",
    "security": "Security",
    "language": "Language"
  }
}

Pluralization

Slang supports pluralization:

{
  "transactionCount": {
    "zero": "No transactions",
    "one": "One transaction",
    "other": "$count transactions"
  }
}

t.transactionCount(count: 5); // "5 transactions"

Date/Number Formatting

Use intl package alongside slang:

import 'package:intl/intl.dart';

final dateFormat = DateFormat.yMMMd().format(transaction.date);
final currencyFormat = NumberFormat.currency(
  symbol: currency.symbol,
).format(amount);

Best Practices

1. Use semantic keys: saveButton not button1
2. Group by feature: home.title, wallet.add
3. Keep base language complete: Always translate all keys
4. Use placeholders: "Hello {name}" not string concatenation
5. Context-aware: Provide context for translators in comments

Changing Default Locale

In main.dart:

void main() {
  WidgetsFlutterBinding.ensureInitialized();

  // Set default locale
  LocaleSettings.useDeviceLocale();

  runApp(ProviderScope(child: DWalletApp()));
}