gen_lang is a dart library for internationalization. Extracts messages
to generate dart files required by

Now, three steps for internationalization

  1. Preparing Json files
  2. Run gen_lang
  3. Use it in coding


Add these libraries into pubspec.yaml

        sdk: flutter 
    gen_lang: 0.1.3


pub run gen_lang:generate

A below table shown all supported arguments:

Argument Description
--source-dir A source folder contains all string json files (defaults to "res/string")
--output-dir A output folder stores all generated files (defaults to "lib/generated")
--template-locale Use string_{template-locale}.json as a template to search KEY. If string_en does not exist, this script will use the first string json file as a template (defaults to "en")

Source of Json Files

By default, the json files are required to locate at res/string. Using
--source-dir argument can change the default source path. These files
must be named in this pattern string_{Locale}.json

Example of the files,

|--- lib 
|--- res 
     |--- string 
         |--- string_en.json 
         |--- string_zh_TW.json 
         |--- string_ja.json 

Supported Message Type

Simple message

Define a json key and message without parameters

    "simpleMessage": "This is a simple Message"

Message with parameters

Define a message with parameters. Use ${parameterName} in a message.

    "messageWithParams": "Hi ${yourName}, Welcome you!"

Plural messages with parameters

Define messages in a plural form. ${how many} is a reserved parameter in
a plural message. This parameters support integer only. For Intl,
Intl.plural() supports these plural keyword including 'Zero', 'One',
'Two', 'Few', 'Many' and 'Other'. Define a json key into this pattern
{jsonKey} {pluralKeyword}. For 'Other', need to define 'POther' for the
plural keyword.


    "pluralMessageZero": "Hi ${interviewerName}, I have no working experience.", 
    "pluralMessageOne": "Hi ${interviewerName}, I have one year working experience.", 
    "pluralMessageTwo": "Hi ${interviewerName}, I have two years of working experience.", 
    "pluralMessageFew": "Hi ${interviewerName}, I have few years of working experience.", 
    "pluralMessageMany": "Hi ${interviewerName}, I worked for a long time.", 
    "pluralMessagePOther": "Hi ${interviewerName}, I have ${howMany} years of working experience."

To know plural rules more, please read
Intl's plural rules
source code.

Gender message with parameters

Define a message in gender form. ${targetGender} is a reserved parameter
in a gender message. This parameters support string value with 'male',
female' and 'other'. For Intl, Intl.gender() supports these keyword
including 'Male', 'Female' and 'Other'. Define a json key into this
pattern {jsonKey} {genderKeyword}. For 'Other', need to define 'GOther'
for the gender keyword.


    "genderMessageMale": "Hi ${name}, He is boy.", 
    "genderMessageFemale": "Hi ${name}, She is girl", 
    "genderMessageGOther": "Hi ${name}, he/she is boy/girl." 

Usage of i18n.dart

The script will generate two files into the output folder including
i18n.dart and messages_all.dart. Import i18n.dart into your source
code. Then finish internationalization tasks.


import 'package:gen_lang_example/generated/i18n.dart';


      localizationsDelegates: [
      supportedLocales: S.delegate.supportedLocales,

        S.of(context).simpleMessage; // Simple Message 
        S.of(context).messageWithParams('developer'); // Message with parameters
        S.of(context).pluralMessage(10, 'King Wu'); // Plural Message with parameters
        S.of(context).genderMessage('male', 'King Wu'); // Gender Message with parameters

Running Script in Example

Go into example folder. Run the command

cd example
pub run gen_lang:generate

Then will generate i18n.dart and messages_all.dart