i69n 0.0.4
i69n: ^0.0.4 copied to clipboard


Simple internationalization tool for Dart and Flutter, based on YAML files and source generation.

Simple internationalization package for Dart and Flutter.

Overview #

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


  save: Save
  load: Load
  welcome(String name): "Hello $name!"
  logout: Logout

Into these generated Dart classes:

class ExampleMessages {
    const ExampleMessages();
    ButtonExampleMessages get button => ButtonExampleMessages(this);
    UsersExampleMessages get users => UsersExampleMessages(this);
class ButtonExampleMessages {
    final ExampleMessages _parent;
    const ButtonExampleMessages(this._parent);
    String get save => "Save";
    String get load => "Load";
class UsersExampleMessages {
    final ExampleMessages _parent;
    const UsersExampleMessages(this._parent);
    String get logout => "Logout";
    String welcome(String name) => "Hello $name!";

... and use them in your code - plain and simple.

ExampleMessages m = ExampleMessages();
// outputs: Hello World!

Package is an extension (custom builder) for https://pub.dartlang.org/packages/build_runner, Dart standard for source generation and it can be used with Flutter, AngularDart or any other type of Dart application.

i69n: 51 points simpler than your standard i18n! #

Motivation and goals #

  • The official Dart/Flutter approach to i18n seems to be ... 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):

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

Write your translations into other YAML files:

exampleMessages_cs.i69n.yaml (_cs = Czech translation)

  done: Hotovo
  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); // output: OK
print(m.generic.done); // output: DONE

m = ExampleMessages_cs();
print(m.generic.ok); // output: OK
print(m.generic.done); // output: Hotovo

Parameters and pluralization #

The implementation is VERY straightforward, which that allows you to do all sorts of crazy stuff:

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

Now see the generated classes:

class ExampleMessages {
    const ExampleMessages();
    InvoiceExampleMessages get invoice => InvoiceExampleMessages(this);        
    ApplesExampleMessages get apples => ApplesExampleMessages(this);
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')}.";

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)}.";

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

There are three functions you can use in your message:

String _plural(int count, {String zero, String one, String two, String few, String many, String other})

String _cardinal(int count, {String zero, String one, String two, String few, String many, String other})

String _ordinal(int count, {String zero, String one, String two, String few, String many, String other})

_plural and _cardinal do the same. I just felt that _plural is a little bit less scary name :-)

We need only two forms of the word apple in English. Apple (one) and apples (many). But in Czech:

  _apples(int cnt): "${_plural(cnt, one:'jablko', few: 'jablka', many:'jablek')}"

See also:

How to use generated classes #

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

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

void main() async {
  ExampleMessages m = ExampleMessages();

  await cs.loadLibrary();
  m = cs.ExampleMessages_cs(); // see? ExampleMessages_cs extends ExampleMessages

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 in this case a singleton would be acceptable also.

How to use with Flutter #

Create YAML file with your messages, for example:


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

    sdk: flutter
  i69n: any

  build_runner: any
    sdk: flutter

Open a terminal and in the 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 rebuilt automatically each time you change the source YAML.

For one-time (re)build of your messages run:

flutter packages pub run build_runner build

Import generated messages and use them:

import 'messages/foo.i69n.dart'


Foo m = Foo();
return Text(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. See example.

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/main.dart and Czech and English implementation.

If you implement support for your language, please let me know, I'll gladly embed it into the package.


  • 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 package repository (https://github.com/fnx-io/i69n) and run:

webdev serve example:8080


pub run build_runner serve example:8080

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

Credits #

Created by https://fnx.io.

pub points



Simple internationalization tool for Dart and Flutter, based on YAML files and source generation.

Repository (GitHub)
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build, build_config, yaml


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