This package is made for R-file code generation using build_runner.

R file contains static access to application asset names and inherited access (via BuildContext) to localized String resources.

With this approach you will not be able to make a typo in any resource name.

How to use

To use the resources code generation add dev dependency in your pubspec.yaml:

  build_runner: <build_runner version here>
  r_resources: ^1.0.0

To generate R-file, run build_runner: flutter pub run build_runner build. r.dart file will be created in lib folder

Plain images and SVG

In order to generate R-names for image assets, you need to follow these steps:

  1. Create assets folder in project root folder (your_app/assets)
  2. Create images folder for plain image files (such as .png, .jpg, etc.). And/Or create svg folder for .svg files.
  3. Add image assets to these folders.
  4. Add assets to pubspec.yaml:

    - assets/images/
    - assets/svg/
  1. Run code generation

Note: to add plain images for different scale factors you may add scaled folders inside images folder.


After r.dart is generated, you can reference assets like follows:


Configuration file

r_resources provides some configuration to code gen.

Add the r_options.yaml config file to project root folder. Example:

path: 'lib/codegen'

generate_strings: true

  - en_US
  - en_GB
  - ru

fallback_locale: en_US


path – parameter describing where r.dart would be saved. Path should always start with lib folder. Equals lib by default.

generate_strings – parameter that turns on and off string resources generation. Equals false by default, since you may use other localized strings gen packages.

supported_locales – parameter describing which locales will be supported by your app. Equals en by default. It is only makes sence to add this parameter when generate_strings is true otherwise it will be ignored.

fallback_locale – parameter describing which locale translations will be used in case of missing translations. Equals en by default. It is only makes sence to add this parameter when generate_strings is true otherwise it will be ignored.


r_resources provides a simple way to generate string translations to your app.

This generation is turned off dy default.

How to use Strings gen

To start generating localized strings resources you should set generate_strings parameter to true in configuration file.

Also you may need to configure supported_locales and fallback_locale parameters.

All locale naming used by codegen is using the following format: <language_code>_<country_code>. country_code may be ommited to use generic language code for all nested countries. Examples: en_GB, ru, en. Note that en_GB is not the same as en.

After you configured generate_strings, supported_locales and fallback_locale parameters, you should add translation files to your_app/assets/strings.

In case you specified r_options.yaml like this:

generate_strings: true

  - en_US
  - en_GB
  - ru

fallback_locale: en_US

then you should add en_US.json, en_GB.json and en_US.json files. And you need to make sure that en_US.json file contains all possible translations, since it will be used as a fallback.

Translations files are single json-s. Field names in different tranlstion files should match.

en_US.json (fallback locale):

    "label_lorem_ipsum": "Lorem ipsum",
    "label_color": "Color",
    "format_example": "Your object is ${object} and other is ${other}",
    "label_with_newline": "HELLO!\nI'm new line symbol (\\n)"


    "label_color": "Цвет",
    "format_example": "Ты передал object = ${object}"

With these files have been used to generate R, you can access localized values in code as follows:


After successfull code generation r.dart will have 2 new classes:

  1. _Strings which instance can be accesed by R.stringsOf(context) and used as localized values container
  2. RStringsDelegate – the LocalizationsDelegate for type _Strings

You should use RStringsDelegate to configure localizations of your app widget:

return MaterialApp(
  supportedLocales: RStringsDelegate.supportedLocales,
  localizationsDelegates: [


This package is also supports localized formatting:

en_US.json (fallback locale):

    "format_example": "Your object is ${object} and other is ${other}"


    "format_example": "Ты передал object = ${object}"

It looks like string interpolation in json files. After generation you will have the following function instead of getter in _Strings class:

String format_example({
  required Object object,
  required Object other,

It can be used in code as follows:

    object: 12345,
    other: 'OTHER',

Planned features

☑ Plain images


☑ String resources

☐ Colors

☐ Text styles

☐ Themes


Licensed under the MIT License.


View Github