asset_pack

==============

Introduction

An asset management library for Dart games. Assets are organized into a tree of asset packs. Assets can be any resource from a simple text string to a complex skinned character.

Typically an asset pack file is loaded from the network, parsed, and all child assets are loaded from the network and imported. An asset pack file is a JSON text file describing the child assets. Asset packs and assets can also be programmatically added.

asset_pack is designed to be extended by third party libraries which provide their own loaders and importers.

Overview

Each asset manager has a tree of asset packs. Each asset pack contains assets and other asset packs. Every asset has a logical asset path, which is a . separated list of strings. Example asset paths follow:

• animals.cats.pic
• animals.kinds
• animals.dogs.pic

Why asset_pack ?

The asset_pack library makes runtime loading of game assets a breeze. Also, the library has friendly developer tools for creating pack files and deep integration with other game libraries for Dart.

Features

• Powerful runtime asset importing.
• Friendly developer tools for building, editing, and listing .pack files.
• API for adding assets programmatically.
• Integration with third party libraries including spectre and simple_audio.

How are assets accessed ?

Imported assets are accessed via the [] operator. The root of the tree is accessed via the root property on an AssetManager. Example:

ImageElement image = assetManager.root['animals.cats.picture'];

Each imported asset also has an associated Asset instance. An Asset holds metadata associated with the imported asset. It can be accessed via the assets map of the AssetPack or getAssetAtPath. Example:

Asset asset = assetManager.getAssetAtPath('animals.cats.picture');

How are assets loaded?

Assets are loaded by loading an asset pack. Each asset listed in an asset pack is loaded via an AssetLoader and then imported by an AssetImporter.

Which loaders and importers come out of the box?

Loaders:

• ArrayBufferLoader
• BlobLoader
• ImageLoader
• TextLoader
• TextMapLoader

Importers:

• JsonImporter
• PackImporter
• TextImporter

I want to add an importer for a new asset type, what do I do?

Implement an AssetImporter and add it to the the importers map of the AssetManager.

I want to add a loader for a new asset type, what do I do?

Implement an AssetLoader and add it to the the loaders map of the AssetManager.

NOTE: In many cases it's unnecessary to write a new loader.

Getting Started

1. Add the following to your project's pubspec.yaml and run pub install.

dependencies:
  asset_pack:
    git: https://github.com/johnmccutchan/asset_pack.git

2. Add the correct import for your project.

import 'package:asset_pack/asset_pack.dart';

Documentation

Key Classes

• AssetPack A set of assets which are loaded and unloaded atomically. May reference other asset packs.
• Asset The meta-data for an asset which has been loaded and imported.
• AssetManager Holds the root of the asset tree.
• AssetLoader A class which loads data from a URL.
• AssetImporter A class which imports data loaded from an AssetLoader.

API

Reference Manual

Samples

Examples

1. Initialize an AssetManager:

main() {
  // Construct a new AssetManager.
  AssetManager assets = new AssetManager();
}

2. Load a pack:

main() {
  // Construct a new AssetManager.
  AssetManager assets = new AssetManager();
  // Load 'explosions' from 'explosions.pack'.
  AssetPack explosions = assets.load('explosions', 'domain/explosions.pack');
}

3. Access a loaded asset:

main() {
  // Construct a new AssetManager.
  AssetManager assets = new AssetManager();
  // Load 'explosions' from 'explosions.pack'.
  AssetPack explosions = assets.load('explosions', 'domain/explosions.pack');
  // Explosions has a 'dynamite' asset which is a sound clip.
  playSound(assets['explosions.dynamite']);
}

4. Programmatically add an asset pack:

main() {
  // Construct a new AssetManager.
  AssetManager assets = new AssetManager();
  // Register the 'test' pack. No url is needed so the empty string suffices.
  AssetPack testPack = assets.registerPack('test', '');
  // testPack and ['test'] are both the same object.
  assert(assets['test'] == testPack);
  Asset testPackAsset = assets.getAssetAtPath('test');
  // The imported field of testPackAsset is testPack.
  assert(testPackAsset.imported == testPack);
}

5. Programmatically load and register an asset:

main() {
  // Construct a new AssetManager.
  AssetManager assets = new AssetManager();
  // Register the 'test' pack. No url is needed so the empty string suffices.
  AssetPack testPack = assets.registerPack('test', '');
  // Register asset 'foo' and load it's contents from 'foo.txt'.
  // The asset type is 'text' and there are no arguments for the loader
  // or importer.
  Future<Asset> futureAsset = testPack.loadAndRegisterAsset('foo', 'foo.txt',
                                                            'text', {}, {})
  futureAsset.then((asset) {
    // Print the contents of foo.txt.
    print(asset.imported);
  });
}