i18n_extension

• When defining your translations, you can now use the modifiers .male(), .female() and .neutral(), and then declare a gender function that calls the provided localizeGender(). For example:

  extension Localization on String {
    static final _t = Translations.byText('en-US') +
      {
        'en-US': 'There is a person'
            .male('There is a man')
            .female('There is a woman'),
        'pt-BR': 'Há uma pessoa'
            .male('Há um homem')
            .female('Há uma mulher'),
      };
  
    String gender(Gender gender) => localizeGender(gender, this, _t);
  }
  

  Then, the UI code can translate it like this:

  'There is a person'.gender(Gender.male); // There is a man
  'There is a person'.gender(Gender.female); // There is a woman
  'There is a person'.gender(Gender.neutral); // There is a person
  

  A gender without a version falls back to the unversioned text, as Gender.neutral does above. This means .neutral() is only needed when the neutral text is not the unversioned text. See Gender modifiers in the README.

• The default import default.i18n.dart now also provides .gender(), which returns the string unchanged, as .plural() does.

• Gender and plural can be combined. To declare all the combinations, nest the plural modifiers inside the gender modifiers, and pass the gender to .plural(), since localizePlural() now accepts an optional gender parameter:

  extension Localization on String {
    static final _t = Translations.byText('en-US') +
      {
        'en-US': 'There is a person'
            .zero('There is nobody')
            .many('There are %d people')
            .male('There is a man'
                .zero('There are no men')
                .many('There are %d men'))
            .female('There is a woman'
                .zero('There are no women')
                .many('There are %d women')),
        'pt-BR': 'Há uma pessoa'
            .zero('Não há ninguém')
            .many('Há %d pessoas')
            .male('Há um homem'
                .zero('Não há homens')
                .many('Há %d homens'))
            .female('Há uma mulher'
                .zero('Não há mulheres')
                .many('Há %d mulheres')),
      };
  
    String plural(value, [Gender? gender]) => localizePlural(value, this, _t, gender: gender);
  }
  

  Use it like this:

  'There is a person'.plural(3, Gender.female); // There are 3 women
  'There is a person'.plural(1, Gender.male); // There is a man
  'There is a person'.plural(0, Gender.neutral); // There is nobody
  

  The plural versions of the given gender are tried first, then the gender version itself (which is the singular, for 1 element), then the plural versions that don't depend on the gender, and finally the unversioned text. So only the combinations that actually differ need to be declared. See Combining gender and plural in the README, and the example in example/lib/11_gender_plural_example/main_gender_plural.dart.

  The file importers support it too. In .json and .yaml files, a gender version may itself be a map of plural versions, with its own other:

  "There is a person": {
    "other": "Hay una persona",
    "zero": "No hay nadie",
    "many": "Hay %d personas",
    "male": { "other": "Hay un hombre", "zero": "No hay hombres", "many": "Hay %d hombres" },
    "female": { "other": "Hay una mujer", "zero": "No hay mujeres", "many": "Hay %d mujeres" }
  }
  

  And:

  "There is a person":
    other: "Hay una persona"
    zero: "No hay nadie"
    many: "Hay %d personas"
    male:
      other: "Hay un hombre"
      zero: "No hay hombres"
      many: "Hay %d hombres"
    female:
      other: "Hay una mujer"
      zero: "No hay mujeres"
      many: "Hay %d mujeres"
  

  In .arb files, a select and a plural may now be nested, one inside the other, which is the ICU way of combining gender and number:

  "people": "{gender, select, male{{count, plural, =0{No hay hombres} one{Hay un hombre} other{Hay # hombres}}} female{{count, plural, =0{No hay mujeres} one{Hay una mujer} other{Hay # mujeres}}} other{{count, plural, =0{No hay nadie} one{Hay una persona} other{Hay # personas}}}}"
  

  The one (or =1) case of a gender becomes the gender version itself (its singular), and the other case of a gender becomes its many version (unless there's a many case) and also its singular, when there's no one case. A plural inside a plural, a select inside a select, and deeper nesting are still not supported.

• In .json and .yaml files, the versions named male, female and neutral are now the gender versions, the same as .male(), .female() and .neutral() in Dart, for .gender(). Likewise, in .arb files, the male, female and neutral cases of an ICU select are now the gender versions:

  "pronoun": "{gender, select, male{él} female{ella} other{ellos}}"
  

  'pronoun'.gender(Gender.male); // él
  'pronoun'.gender(Gender.neutral); // ellos (the `other` case)
  

  The files themselves don't change. What changes is how you read those versions in Dart: before, you'd use .version('male'), and now you use .gender(Gender.male). Versions and select cases with any other name still work with .version(), as before.

• In .po files, the entries with the contexts male, female and neutral (like msgctxt "male") are now the gender versions of the entry with the same msgid, for .gender(), and a gender entry may have msgid_plural, to combine gender and plural, for .plural(count, gender). Before, the contexts were ignored. Entries with any other context are still read as if they had no context. See Plurals and genders in PO files.

• Fixed: .times(10, text) is now the same as .ten(text). Before, .plural(10) didn't find it, since it looks for the ten version.

• Note: This is a major version because the new names are likely to clash with client code that implemented its own gender modifiers.

• Translations can now also be loaded from YAML files, with Translations.byFile() and Translations.byHttp(). Files ending with .yaml or .yml are loaded in the same way as .json and .po files, with the language tag taken from the file name. Each file must contain a map of translation keys to translations, where each translation is text, or a map of its versions, like plurals and genders (see the next item):

  Welcome to this demo.: Bienvenido a esta demostración.
  "i18n Demo": Demostración i18n
  "You clicked the button %d times:":
    other: "Hiciste clic en el botón %d veces:"
    zero: "No hiciste clic en el botón:"
    one: "Hiciste clic en el botón una vez:"
    12: "Hiciste clic en el botón una docena de veces:"
  

  Comments, quoted and unquoted text, anchors, and the multiline styles (| and >) are supported. Note that in YAML an unquoted 123, true or empty value is read as a number, a boolean or null, not as text, so quote those (except the integer versions, like the 12 above, which may be unquoted). Lists are not allowed. A file that breaks these rules fails with a clear error, or is skipped when failOnInvalidResource is false.

  The new loaders are I18nYamlLoader() (for .yaml) and I18nYamlLoader.yml() (for .yml), and both are included in I18n.loaders by default.

• In .json and .yaml files, a translation may now be a map of versions, for plurals and genders. This is the same as using the string modifiers .zero(), .one(), .times(), .many(), .modifier() etc. in Dart. The other version is required, and is the text used when no other version applies (in Dart, the string the modifiers are called on). For example:

  {
    "You clicked the button %d times:": {
      "other": "Hiciste clic en el botón %d veces:",
      "zero": "No hiciste clic en el botón:",
      "one": "Hiciste clic en el botón una vez:",
      "12": "Hiciste clic en el botón una docena de veces:"
    },
    "There is a person": {
      "other": "Hay una persona",
      "male": "Hay un hombre",
      "female": "Hay una mujer"
    }
  }
  

  The plural versions are zero, one, two, three, four, five, six, ten, twoThreeFour, oneOrMore, zeroOne and many, plus any integer, like 12, which is the same as .times(12). Any other name, like male, is a version for .version(). Each version must be text (versions can't be nested), and a map without other, or with two versions that mean the same, like one and 1, fails with a clear error. In YAML, the versions are nested keys, as in the YAML example above.

  The encoding is done by the base I18nLoader, when the decoded translations are checked, so custom loaders whose decode() returns maps of versions get it too.

• Translations can now also be loaded from ARB files (.arb), the format used by Flutter's own gen-l10n tool and by most translation services, with Translations.byFile() and Translations.byHttp(). The new loader is I18nArbLoader(), included in I18n.loaders by default.

  The locale comes from the @@locale attribute, or else from the file name, which may be the locale itself (es-ES.arb, es_ES.arb) or end with it after an underscore, as Flutter names them (app_es.arb, intl_messages_pt_BR.arb, app_zh_Hans_CN.arb). The @@ attributes and the @key metadata are ignored, as they are for translators and tools. The ICU messages are converted to the format of this package:

  {
    "@@locale": "es",
    "welcome": "Bienvenido, {name}",
    "itemCount": "{count, plural, =0{Sin artículos} one{Un artículo} other{# artículos}}",
    "pronoun": "{gender, select, male{él} female{ella} other{ellos}}"
  }
  

  • Placeholders like {name} or {0} are kept, to be filled with .args(). Formatted placeholders, like {price, number, currency} or {date, date, ::yMd}, become simple placeholders, like {price}, since the loader doesn't format values: pass them already formatted to .args().

  • A plural becomes a translation with plural versions, for .plural(count). Both # and the plural variable become the number. The cases =0/zero, =1/one, =2/two, few, many, =N and other become the versions .zero(), .one(), .two(), .twoThreeFour(), .many(), .times(N) and the default text. The plural may be part of a longer message, in which case each version contains the whole message.

  • A select (like a gender) becomes a translation with versions, for .version(case), with other as the default text.

  • A message may contain a single plural or select, and not one inside the other, since .plural() and .version() select a translation by a single value. Such messages, and the plural offset, fail to load with an error that explains the problem.

  • By default there's no escaping, as in gen-l10n: an apostrophe is just an apostrophe. For files written with use-escaping: true, where '' is an apostrophe and text between single quotes is literal, use I18nArbLoader(useEscaping: true):

    I18n.loaders.removeWhere((loader) => loader() is I18nArbLoader);
    I18n.loaders.add(() => I18nArbLoader(useEscaping: true));
    

• Translations.byFile() and Translations.byHttp() have two flags that control what happens when a single file or resource fails to load. Both default to true, which fails the whole load, so that no translations are loaded at all:

  • failOnMissingResource applies to a file or resource that cannot be read: a 404 or network error, or an asset that fails to load (which on the web is a download).

  • failOnInvalidResource applies to a file or resource that was read, but cannot be decoded (invalid JSON, YAML, ARB or ICU message), or has invalid content, like a value that is not a String.

  When a flag is false, that kind of failure is reported to I18n.failedResourceCallback and skipped, while the other files or resources still load. The error is a MissingTranslationsResourceException or an InvalidTranslationsResourceException (both are TranslationsExceptions), which carry the resource that failed and the underlying error, so the callback can tell them apart and log the problem file without parsing the message. The I18nLoader.fromAssetDir() and fromUrl() methods have the same two flags.

  This requires i18n_extension_core 5.2.0.

• The loader classes I18nLoader, I18nJsonLoader, I18nPoLoader, I18nYamlLoader and I18nArbLoader are now exported by the package, so that you can configure them or extend I18nLoader without importing the src files.

• Loaders may now override I18nLoader.decodeFile(), which receives the file name and its content, and returns both the translations and the language tag. The default implementation calls decode() and takes the language tag from the file name, so custom loaders that only override decode() keep working.

• Translations.byFile() now also works on the web. Previously, it did nothing there, so the app showed the default-locale strings, and the only way to load translation files on the web was Translations.byHttp(), listing each file by name.

  There was no technical reason for that restriction. Translations.byFile() doesn't read the user's file system, but the assets bundled with the app, and on the web Flutter downloads those from the web server that hosts the app, like it does with images and fonts. The list of files also comes from the asset manifest, which Flutter provides on the web too. So the same code now works on all platforms, including scanning the directory and its subdirectories for .json and .po files.

  On the web, the default timeout of load() for Translations.byFile() is 1 second, the same as for Translations.byHttp(), instead of 0.5 seconds, since the files are downloaded. As before, if the timeout is reached, the load continues in the background, and the widgets rebuild when it finishes.

• Fixed the way the I18n widget picks the app locale from the list of locales set in the device settings, when the user's preferred language is supported only in a different regional variant.

  The device provides its locales in order of user preference, for example [pt-PT, en-US]. Since version 15.1.1, the widget would pick the first device locale that exactly matched one of the supportedLocales, so with supportedLocales: [pt-BR, en-US] the app would show English, even though the user prefers Portuguese. The same happened with device locales [zh-Hans-GB, en] and supportedLocales: [zh, en], which resolved to en instead of zh.

  Now, the widget prefers a different variant of the user's preferred language, over the user's second language, so the examples above resolve to pt-BR and zh. For each device locale, in order, it looks for a supported locale that matches it exactly, then by language and script, then by language and country, and then by language only. This uses Flutter's basicLocaleListResolution, the same algorithm MaterialApp uses by default, and the one versions 13.x relied on. Also, if no device language is supported at all, the app locale is now the first supported locale (previously, the unsupported first device locale was used), so list your default locale first.

• The locale resolution is now configurable, through the new localeResolver parameter of the I18n widget. The default is I18n.languageMatchResolver, described above. The previous behavior is available as I18n.exactMatchResolver:

  I18n(
    supportedLocales: ['pt-BR'.asLocale, 'en-US'.asLocale],
    localeResolver: I18n.exactMatchResolver, // Restores the previous behavior.
    child: AppCore(),
  );
  

  You may also provide your own resolver function, which receives the device locales and the supported locales, and returns the locale the app should use. See the "Locale resolution" section of the README for details.

• Translations.byFile() and Translations.byHttp() now accept an optional failOnMissingResource parameter. It defaults to true, which keeps the previous behavior: if a single file or resource fails to load, the whole load fails, and no translations are loaded at all.

  When you set it to false, the file or resource that failed is logged and skipped, and the ones that loaded correctly are kept. This is useful when a language file is temporarily unavailable or broken, and you'd rather show the other languages than none. If all of them fail, no error is thrown either, and your app simply shows the default-locale strings:

  static final _t = Translations.byHttp('en-US',
    url: 'https://example.com/translations',
    resources: ['en-US.json', 'es.json', 'pt-BR.po', 'fr.po'],
    failOnMissingResource: false, // Keep the resources that loaded correctly.
  );
  

  For Translations.byFile(), the files are listed from the asset manifest, so they can't really be missing. In that case, what's skipped are files that can't be read from the asset bundle, files that can't be decoded (for example, invalid JSON), and files containing values that are not Strings. A file is either fully loaded or fully skipped.

  By default, a skipped file or resource is printed to the console, together with the error. You may customize this by setting I18n.failedResourceCallback, which receives the specific asset path or url that failed, plus the error:

  I18n.failedResourceCallback = (resource, error) {
    myCrashReporting.log('Could not load $resource: $error');
  };
  

• Translations.byFile() now only loads the files inside the given dir (and its subdirectories). Previously, dir: 'assets/translations' would also load files from sibling directories that merely start with the same text, like assets/translations_old/. To that end, a trailing slash is now automatically added to dir, if it's missing.

• See examples 9_load_by_file_skip_errors_example and 10_load_by_http_skip_errors_example.

• Fixed I18n.preInitializationLocale to Locale('en', 'US'). This is only used for the brief period when the app starts.

• Fixed multi-locale fallback to properly handle device language preferences. The system now correctly checks all device locales (not just the first) against all supported locales. When a device has multiple language preferences (e.g., French primary, German secondary), and the primary language is not supported but a secondary language is, the app will now correctly use the first supported language from the device's preference list.

• Optionally, you can now set the supportedLocales of your app in the I18n widget. For example, if your app supports American English and Standard Spanish, you'd use: supportedLocales: [Locale('en', 'US'), Locale('es')], or supportedLocales: ['en-US'.asLocale, 'es'.asLocale].

  If you do set I18n.supportedLocales, you must add the line supportedLocales: I18n.supportedLocales to your MaterialApp (or CupertinoApp) widget, like this:

  void main() {
    WidgetsFlutterBinding.ensureInitialized();
  
    runApp(I18n(
        initialLocale: ...,
        supportedLocales: ['en-US'.asLocale, 'es'.asLocale], // Here!
        localizationsDelegates: [ ... ],
        child: AppCore(),
      ));
    }
  }
  
  class AppCore extends StatelessWidget {
    Widget build(BuildContext context) {
      return MaterialApp(
        locale: I18n.locale,
        supportedLocales: I18n.supportedLocales, // Here!
        localizationsDelegates: I18n.localizationsDelegates,
        ...
      ),
  

  By providing I18n.supportedLocales, only those supported locales will be considered when recording missing translations. In other words, unsupported locales will not be recorded as missing translations.

• Breaking Change: The Translations.missingTranslationCallback signature has changed. This will only affect you if you've defined your own callback, which is unlikely. If your code does break, just update it to the new signature, which is an easy fix. Also, note that it now returns a boolean. Only if it returns true, the missing translation be recorded to the Translations.missingTranslations map.

Version 14 brings important improvements, like new interpolation methods, useful extensions, improved standardization, and loading translations from files and from the web, with the cost of a few breaking changes that are easy to fix. Please, follow the instructions below to upgrade your code.

• Breaking Change: Now, you must have a single (no more than one) I18n widget in your entire widget tree, and it must always be put ABOVE the MaterialApp (or CupertinoApp) widget, in the tree. There, it will be able to provide translations to all your routes and dialogs.

• Breaking Change: You must now add the line locale: I18n.locale to your MaterialApp (or CupertinoApp) widget, like this:

  MaterialApp(
     locale: I18n.locale,
     ...      
  

• Breaking Change: Because of the way Flutter works, you have to make sure your I18n widget is NOT declared in the same widget as the MaterialApp, but in a parent widget. For example, this is WRONG:

  Widget build(BuildContext context) {
    return I18n( // Wrong!
      child: MaterialApp(
        home: MyScreen(),
  

  Instead, this is how your main.dart file could look like:

  import 'package:i18n_extension/i18n_extension.dart';
  import 'package:flutter_localizations/flutter_localizations.dart';
         
  void main() {
    WidgetsFlutterBinding.ensureInitialized();
    runApp(MyApp());
  }
  
  class MyApp extends StatelessWidget {
    Widget build(BuildContext context) {
      return I18n( // I18n in a parent widget!
        child: AppCore(),
      );
    }
  }
  
  class AppCore extends StatelessWidget {
    Widget build(BuildContext context) {
      return MaterialApp( // MaterialApp is here!
        locale: I18n.locale, // Locale declaration is here!
        localizationsDelegates: [ ... ],
        supportedLocales: [ ... ],
        home: ...
      ),
  

  Another good alternative is declaring the I18n widget directly inside the runApp call, in your main function:

  void main() {
    WidgetsFlutterBinding.ensureInitialized();
    runApp(I18n(child: AppCore())); // I18n in a parent widget!
  }
  
  class AppCore extends StatelessWidget {
    Widget build(BuildContext context) {
      return MaterialApp( // MaterialApp is here!
        locale: I18n.locale, // Locale declaration is here!
        localizationsDelegates: ...
      ),
  

• Breaking Change: The MaterialApp (or CupertinoApp) widget contains, internally, a Localizations widget, which is used by Flutter to provide translations to all native Flutter widgets. The I18n widget will now automatically keep in sync with this Localizations widget, so that when you change the locale in I18n (with context.locale = 'en-US'.asLocale, for example), it will also change automatically in the Localizations widget. This means that Localizations.of(context).locale will always return the same result as I18n.of(context).locale, as context.locale, and as I18n.locale.

  If you previously had your own logic to change the native Localizations locale by changing the locale parameter of the MaterialApp widget, you can now remove it, as this is not necessary anymore.

• Breaking Change: Language codes must now respect the BCP47 standard, when you define your translations.
  For example, you should now use en-US instead of the old en_us format. Other valid code examples are: en, es-419, hi-Deva-IN and zh-Hans-CN.

  This is an example of a WRONG translation definition:

  // Will throw: Locale "en_us" should be "en-US" 
  Translations.byText('en_us') + // Wrong!
     {
        'en_us': 'Hello, how are you?',  // Wrong!
        'pt_br': 'Olá, como vai você?',  // Wrong!
        'es': '¿Hola! Cómo estás?',
        'fr': 'Salut, comment ca va?',
        'de': 'Hallo, wie geht es dir?',
     };
  

  To help you upgrade, a TranslationsException error will be thrown when you use the old code format. The error message will be something like: Locale "en_us" should be "en-US"

  This is an example of a VALID and correct translation definition:

  Translations.byText('en-US') +
     {
        'en-US': 'Hello, how are you?',
        'pt-BR': 'Olá, como vai você?',
        'es': '¿Hola! Cómo estás?',
        'fr': 'Salut, comment ca va?',
        'de': 'Hallo, wie geht es dir?',
     };
  

  Note: If your translations are defined manually in the code, you can quickly fix this by doing a few Search and Replace commands in your IDE to fix the language codes, one for each of your supported languages, for example, replacing 'en_us' with 'en-US' etc.

• New extension Locale.format can be used to return the string representation of the Locale as a valid BCP47 language tag (compatible with the Unicode Locale Identifier (ULI) syntax). If the locale is not valid, format may return an invalid tag, or may return string "und" (undefined).
  The language code, script code, and country code will be separated by a hyphen, and any lowercase/uppercase issues will be fixed. For example:

  var locale = Locale('en', 'us');
  print(locale.format()); // en-US, which is a valid BCP47 language tag
  print(locale.toString()); // en_US
  print(locale.toLanguageTag()); // en-us
  

  Using format is recommended over toString and toLanguageTag (both natively provided by the Locale class). In more detail:

  • Locale.format() returns the string representation of the Locale as a valid BCP47 language tag, fixing any lowercase/uppercase issues and separating components with a hyphen. Allows specifying a different separator. For example, Locale('en', 'us').format() returns en-US, and Locale('en', 'US').format(separator: '|') returns en|US.

  • Locale.toString() returns the language, script and country codes separated by an underscore. For example, Locale('en', 'us').toString() returns en_us and Locale('en', 'US').toString() returns en_US.

  • Locale.toLanguageTag() returns the language code and the country code separated by a hyphen, but does not fix case. For example, Locale('en', 'us').toLanguageTag() returns en-us, and Locale('en', 'US').toLanguageTag() returns en-US.

• New extension String.asLocale can be used to convert a String containing a BCP47 language tag to a Locale object. For example: Locale locale = 'pt-BR'.asLocale;. If the string is not a valid BCP47 language, asLocale will try to fix it. For example, the following lines are all equivalent and result in the same locale:

  var locale = Locale('en', 'US'); 
  var locale = 'en-US'.asLocale; 
  var locale = 'en_US'.asLocale; 
  var locale = 'en-us'.asLocale; 
  var locale = 'EN-US'.asLocale; 
  var locale = 'en US'.asLocale; 
  var locale = 'en|US'.asLocale; 
  var locale = 'en.uS'.asLocale; 
  var locale = 'eN,US'.asLocale; 
  var locale = 'en;US'.asLocale; 
  var locale = 'en, US'.asLocale; 
  

  However, it will only fix the most common errors, by fixing lowercase/uppercase issues, removing spaces, and converting all these separators: - _ | . , ; to hyphens. If it can’t fix it, it will return an invalid Locale, or maybe Locale('und'), meaning the locale is undefined.

  Note that String.asLocale can be used whenever you previously used Locale constructors. For example, instead of:

  supportedLocales: [
    Locale('en', 'US'),
    Locale('es', 'ES'),
  ],
  

  You can now write:

  supportedLocales: [
    'en-US'.asLocale,
    'es-ES'.asLocale,    
  ],
  

• New extension String.asLanguageTag can be used to try and normalize String language tags to the BCP47 standard (which is compatible with the Unicode Locale Identifier (ULI) syntax). It fixes casing (uppercase and lowercase), removes spaces, and turns underscores into hyphens. As such, it can be used to convert the old format language tags to the new ones. For example: 'en_us'.asLanguageTag returns 'en-US'.

• Interpolations. You can now do string interpolations by replacing placeholders with values, with the args function:

  // Hello John and Mary
  'Hello {} and {}'.i18n.args('John', 'Mary');
  
  // Also works with iterables
  'Hello {} and {}'.i18n.args(['John', 'Mary']);
  
  // Named placeholders
  'Hello {name} and {other}'.i18n.args({'name': 'John', 'other': 'Mary'});
  
  // Numbered placeholders
  'Hello {1} and {2}'.i18n.args({1: 'John', 2: 'Mary'});
  
  // And you can mix placeholder types
  'Hello {name}, meet with {} and {other} to explore {1} and {2}.'.i18n.args('Charlie', {'name': 'Alice', 'other': 'Bob'}, {1: 'Paris', 2: 'London'});
  

  For all the details, check the README.md file.

• Breaking Change: Previously, you could also do string interpolation by using sprintf specifiers, like %s, %1$s, %d etc., and providing a list of values to fill them. This is still supported:

  // Hello John and Mary
  'Hello %s and %s'.i18n.fill(['John', 'Mary']);
  
  // Hello John and Mary
  'Hello %1$s and %2$s'.i18n.fill(['John', 'Mary']);  
  
  // Hello Mary and John  
  'Hello %2$s and %1$s'.i18n.fill(['John', 'Mary']);  
  

  However, you can now also provide the values directly, without having to wrap them in a list:

  'Hello %s and %s'.i18n.fill('John', 'Mary');
  'Hello %1$s and %2$s'.i18n.fill('John', 'Mary');
  'Hello %2$s and %1$s'.i18n.fill('John', 'Mary');
  

  The breaking change part of it is that, previously, if you wanted to use the fill extension you needed to declare it yourself in your translations files. Now, that's not necessary anymore, as this extension is provided out of the box. For this reason, if you declared the fill extension yourself, you now need to remove it. Otherwise, the compiler will complain that the extension is declared twice. If you still want to keep your old declaration, change its name.

• Auto saving the locale. Some apps may allow the user to change the language/locale of the app, from inside the app. You'd usually create some widget that presents the list of available locales, and then set it with context.locale = 'es-ES'.asLocale; or similar.

  If you want that user choice to be saved between app restarts, simply set the autoSaveLocale parameter to true:

  I18n(
    autoSaveLocale: true,
    child: AppCore(),
    ...
  

  This will automatically save changes to the locale in the device's storage (shared preferences), and restore it when the app restarts. Note the locale is read asynchronously, which may result in a one frame flicker of the default system locale, before the saved locale is restored. If you want to avoid this flicker, you can explicitly preload the locale yourself by doing initialLocale: await I18n.loadLocale() when the app starts.

  void main() async {
    WidgetsFlutterBinding.ensureInitialized();
   
    runApp(
      I18n(
        initialLocale: await I18n.loadLocale(),
        autoSaveLocale: true, 
        child: AppCore(),    
        ...
  

  Note: While usually not needed, you can also manually load, save and delete the locale from the shared preferences, at any later time, by using the provided static functions: var locale = await I18n.loadLocale(), I18n.saveLocale(locale) and I18n.deleteLocale().

• You can get the current locale by using the context:

  Locale locale = context.locale;
  Locale locale = I18n.of(context).locale;
  

  However, you can also get the locale statically, allowing you to use it in non-widget code:

  // Get a `Locale` object, like Locale('en', 'US') 
  Locale locale = I18n.locale;
  
  // Or get a BCP47 language tag string, like 'en-US'
  String languageTag = I18n.languageTag;
  String languageTag = I18n.locale.format();
  
  // Or get a locale string with a specific separator, like 'en|US'
  String languageTag = I18n.locale.format(separator: '|');
  
  // Or get only the lowercase language code part of the locale, like 'en'.
  String language = I18n.language;
  

  Note, using I18n.localeStr is deprecated. It returns a lowercase string with underscores, like en_us.

• To change the current locale, do this:

  context.locale = Locale('pt', 'BR');
  
  // Or
  context.locale = 'pt-BR'.asLocale;
  
  // Or
  I18n.of(context).locale = 'pt-BR'.asLocale;
  

  To reset the current locale back to the default system locale, do this:

  context.locale = null;
  
  // Or
  context.resetLocale();
  
  // Or
  I18n.of(context).locale = null;
  
  // Or
  I18n.of(context).resetLocale();
  

  Note, any of the above will change the current locale for your widgets using the i18n_extension, and also for native Flutter widgets.

• Breaking Change: The fallback rules changed a little bit. What happens when you don’t provide the translations for the current locale? For example, suppose your current locale is Spanish, but you have only provided translations for English and French. Fallback behavior is now more intuitive and aligned with common sense. In most cases, it will do exactly what you’d expect. However, if you want all the details, check the README.md file.

• Load translations from files or the web.

  If you want to load translations from .json files in your assets directory, create a folder and add some translation files like this:

  assets
  └── translations
      ├── en-US.json
      ├── es-ES.json
      ├── zh-Hans-CN.json
      └── pt.json  
  

  You can also use .po files:

  assets
  └── translations
      ├── en-US.po
      ├── es-ES.po
      ├── zh-Hans-CN.po
      └── pt.po  
  

  Don't forget to declare your assets directory in your pubspec.yaml:

  flutter:
    assets:
      - assets/translations/
  

  Then, you can load the translations using Translations.byFile():

  extension MyTranslations on String {
    static final _t = Translations.byFile('en-US', dir: 'assets/translations');     
    String get i18n => localize(this, _t);  
  }
  

  The above code will asynchronously load all the translations from the .json and .po files present in the assets/translations directory, and then rebuild your widgets with those new translations.

  Similarly, Translations.byHttp() allows you to load translations from .json or .po files in the web. Use it like this:

  extension MyTranslations on String {
  
    static final _t = Translations.byHttp('en-US', 
      url: 'https://example.com/translations', 
      resources: ['en-US.json', 'es.json', 'pt-BR.po', 'fr.po']);
    );
       
    String get i18n => localize(this, _t);  
  }       
  

  IMPORTANT: Since rebuilding widgets when the translations finish loading can cause a visible flicker, you can optionally avoid that by preloading the translations before running your app. To that end, first create a load() method in your MyTranslations extension:

  extension MyTranslations on String {
    static final _t = Translations.byFile('en-US', dir: 'assets/translations');  
    String get i18n => localize(this, _t);  
    
    static Future<void> load() => _t.load(); // Here!  
  }
  

  And then, in your main() method, call MyTranslations.load() before running the app:

  void main() async {
    WidgetsFlutterBinding.ensureInitialized();
    
    await MyTranslations.load(); // Here!
    
    runApp(
      I18n(
        initialLocale: await I18n.loadLocale(),
        autoSaveLocale: true,
        child: AppCore(),
      ),
    );
  }
  

  Another alternative is using a FutureBuilder:

  return FutureBuilder(
    future: MyTranslations.load(),
    builder: (context, snapshot) {
      if (snapshot.connectionState == ConnectionState.done) {
      return MyWidget(...);
    } else {
      return const Center(child: CircularProgressIndicator());
    } ...
  

  Try running the <a href="https://github.com/marcglasberg/i18n_extension/blob/master/example/lib/6_load_by_file_example/main.dart"> load by file example</a>, and
  the <a href="https://github.com/marcglasberg/i18n_extension/blob/master/example/lib/7_load_by_http_example/main.dart"> load by http example</a>, and the

• Compatible with Flutter 3.22.0 and Dart 3.4.0

• The importer library developed by Johann Bauer is now independently available as a standalone package. You can find it at https://pub.dev/packages/i18n_extension_importer. This new package offers capabilities for importing translations in both .PO and .JSON formats. It also includes the GetStrings exporting utility, which is a useful script designed to automate the export of all translatable strings from your project.

• Removed unused packages that were previously used by the removed importer.

• Flutter 3.10 e Dart 3.0.0

• Removed the importer library developed by Johann Bauer, so that users of i18n_extension don’t need to import the analyzer and other unnecessary dependencies. See version [10.0.2] above.

• Breaking change: Removed dependency on analyzer and gettext_parser. The getStrings doesn’t work in this version.

• Analyzer and sprintf version bump.

• Analyzer version bump.

• Flutter 3.0

• The localizePlural method now accepts any object (not only an integer anymore). It will convert that object into an integer, and use that result. Se the method documentation for more information. To make use of it, you may declare your plural() methods as String plural(value) => localizePlural(value, this, _t); from now on. Example: 'This is one item'.plural(2) is now the same as writing 'This is one item'.plural('2').

• Bump version. Docs improvement.

• .po importer fix.