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gen_lang

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

Now, three steps for internationalization

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

Installation

Add these libraries into pubspec.yaml

dependencies: 
    flutter_localizations: 
        sdk: flutter 
dev_dependencies:
    gen_lang: 0.1.3

Usage

pub run gen_lang:generate

A below table shown all supported arguments:

ArgumentDescription
--source-dirA source folder contains all string json files (defaults to "res/string")
--output-dirA output folder stores all generated files (defaults to "lib/generated")
--template-localeUse 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.

Example

{ 
    "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.

Example

{ 
    "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.

Example

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

...

MaterialApp(
      localizationsDelegates: [
        S.delegate,
        GlobalMaterialLocalizations.delegate,
        GlobalWidgetsLocalizations.delegate
      ],
      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

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