Start

Setup

• Dart SDK 3.12+
• A normal Flutter / Dart package (pubspec.yaml at the root)

Install

dev_dependencies only. No runtime API.

dart pub add --dev fast_dev
dart pub add --dev build_runner   # skip if CLI-only

Or by hand:

dev_dependencies:
  fast_dev: ^0.0.1-beta.1
  build_runner: ^2.7.2

Skip build_runner if you only run dart run fast_dev gen. If the project already uses build_runner, adding fast_dev is enough.

Assets still go in pubspec.yaml. Directories are expanded recursively, so one line is usually enough:

flutter:
  assets:
    - assets/

Or list files:

flutter:
  assets:
    - assets/images/logo.svg
    - assets/data/hello.json

Create a config file

Put fast_dev_config.yaml next to pubspec.yaml.

The tool can run without it and will use defaults (the CLI mentions that). A file in the repo is clearer: class name, style, and output are visible to everyone.

A small start:

version: 1

generate:
  output: lib/gen/fast_dev/
  line_length: 80
  assets:
    class_name: Assets
    style: nested

If you have light / dark or locale folders, turn variants on. Something like example/:

version: 1

generate:
  output: lib/gen/fast_dev/
  line_length: 80
  assets:
    class_name: Assets
    style: nested
    variants:
      theme:
        enabled: true
      locale:
        enabled: true
        folders:
          - zh
          - en
        fallback: file

How to create and load the file: Configuration. Field details: Assets. After you write the file:

dart run fast_dev config

Generate

dart run fast_dev gen

Default output is lib/gen/fast_dev/assets.gen.dart.

If the project already uses build_runner, one watch is enough. It runs with the other builders:

dart run build_runner watch

How to sit next to them, and build.yaml: build_runner.

Use

import 'package:your_app/gen/fast_dev/assets.gen.dart';

Image.asset(Assets.images.logo);
rootBundle.loadString(Assets.data.hello);

// after theme / locale variants are on
Image.asset(Assets.images.logo.of(context));

AssetPath is a String. Image.asset, rootBundle, and your own APIs can take it as-is.

A small app lives in example/. API details: Assets.