i69n 0.0.2

Alternative i18n for Dart and Flutter, based on YAML files and source generation.

Alternative internationalization package for Dart and Flutter.

Write your messages into YAML files, and let this package generate a Dart objects from those files.

WARNING: Not battle tested yet! Also the documentation is rather rudimentary. It's more or less a proof of concept. But seems promising.

i69n: 51 points better than i18n!

(nice!)

Motivation

• The official Dart/Flutter approach to i18n seems ... complicated and kind of ... heavyweight.
• I would like my messages to be checked during compile time - is that message really there? Key to the localized message should not be just some arbitrary String, it should be a getter method!
• And if the message takes some parameters, the method should take those parameters!
• I like to bundle messages into thematic groups, the i18n tool should support that and help me with it
• Dart has awesome string interpolation, I want to leverage that!
• I like build_runner and code generation.
• I love the name. i69n is hilarious.

Solution

Write your messages into a YAML file:

exampleMessages.i69n.yaml (default messages):

generic:
  ok: OK
  done: DONE
invoice:
  create: Create invoice
  delete: Delete invoice

Write your translations into other YAML files:

exampleMessages_cs.i69n.yaml (_cs = Czech translation)

generic:
  done: Hotovo
invoice:
  create: Vytvořit fakturu
  delete: Smazat fakturu

... run the webdev tool, or build_runner directly, and use your messages like this:

ExampleMessages m = ExampleMessages();
print(m.generic.ok);
print(m.generic.done);

Parameters and pluralization

The implementation is VERY straightforward, which allows you to do a lot of crazy stuff:

generic:
  ok: OK
  done: DONE
invoice:
  create: Create invoice
  delete: Delete invoice
  help: "Use this function
  to generate new invoices and stuff.
  Awesome!"
  count(int cnt): "You have created $cnt ${_plural(cnt, one:'invoice', many:'invoices')}."
apples:
  _apples(int cnt): "${_plural(cnt, one:'apple', many:'apples')}"
  count(int cnt): "You have eaten $cnt ${_apples(cnt)}."

Maybe it will help, if I show you the generated classes:

class ExampleMessages {
    const ExampleMessages();
    GenericExampleMessages get generic => GenericExampleMessages(this);
    ApplesExampleMessages get apples => ApplesExampleMessages(this);
    InvoiceExampleMessages get invoice => InvoiceExampleMessages(this);
}

class GenericExampleMessages {
    final ExampleMessages _parent;
    const GenericExampleMessages(this._parent);
    String get ok => "OK";
    String get done => "DONE";
}

class ApplesExampleMessages {
    final ExampleMessages _parent;
    const ApplesExampleMessages(this._parent);
    String _apples(int cnt) => "${_plural(cnt, one:'apple', many:'apples')}";
    String count(int cnt) => "You have eaten $cnt ${_apples(cnt)}.";
}

class InvoiceExampleMessages {
    final ExampleMessages _parent;
    const InvoiceExampleMessages(this._parent);
    String get create => "Create invoice";
    String get help => "Use this function to generate new invoices and stuff. Awesome!";
    String get delete => "Delete invoice";
    String count(int cnt) => "You have created $cnt ${_plural(cnt, one:'invoice', many:'invoices')}.";
} 

See how you can reuse the pluralization of _apples(int cnt). (nice!)

How to decide what translation to use (ExampleMessages_cs?, ExampleMessages_hu?) is up to you. The package simply generates message objects, that's all.

import 'exampleMessages.i69n.dart';
import 'exampleMessages_cs.i69n.dart' deferred as cs;

void main() async {
  ExampleMessages m = ExampleMessages();
  print(m.apples.count(1));
  print(m.apples.count(2));
  print(m.apples.count(5));

  await cs.loadLibrary();
  m = cs.ExampleMessages_cs(); // see? ExampleMessages_cs extends ExampleMessages
  print(m.apples.count(1));
  print(m.apples.count(2));
  print(m.apples.count(5));

}

Where and how to store instances of these message classes - again, up to you. I would consider ScopedModel for Flutter and registering messages instance into dependency injection in AngularDart, but that's just me.

Custom pluralization

The package can correctly decide between 'one', 'few', 'many', etc. only for English and Czech (for now). But you can easily plug your own language, see example/index.dart. If your implement support for your language, please let me know, I'll gladly embed it into the package.

See also:

• http://cldr.unicode.org/index/cldr-spec/plural-rules
• https://www.unicode.org/cldr/charts/latest/supplemental/language_plural_rules.html

How to use with Flutter

Create YAML file with your messages, for example:

lib/messages/foo.i69n.yaml

Add build_runner as a dev_dependency and i69n as a dependency to pubspec.yaml:

dependencies:
  flutter:
    sdk: flutter
  i69n: any
  ...

dev_dependencies:
  build_runner: any
  flutter_test:
    sdk: flutter

Open a terminal and in a root of your Flutter project run:

flutter packages pub run build_runner watch

... and keep it running. Your message classes will appear next to YAML files and will be rebuild each time you change source YAML files.

For one-time rebuild of messages run:

flutter packages pub run build_runner build

Then import generated messages and use them:

import '/messages/foo.i69n.dart'

...

Foo m = Foo();
print(m.bar);
...

How to use with AngularDart

You are probably using webdev tool already, so you just need to add i69n as a dependency and that's all.

TODO

• More detailed docs.
• Use it in some of our projects for real.
• Current limitation: default language must be english
• TODO: support custom imports

Example

See example. Clone the repository and run:

webdev serve example:8080

or

pub run build_runner serve example:8080

Now open the browser http://localhost:8080/ and watch the dev tools console.