Lawndart

A unified, asynchronous, easy-to-use library for offline-enabled browser-based web apps. Kinda sorta a port of Lawnchair to Dart, but with Futures and Streams.

Lawndart uses Futures to provide an asynchronous, yet consistent, interface to local storage, indexed db, and websql. This library is designed for simple key-value usage, and is not designed for complex transactional queries. This library prefers simplicity and uniformity over expressiveness.

You can use this library to help deal with the wide array of client-side storage options. You should be able to write your code against the Lawndart interface and have it work across browsers that support at least one of the following: local storage, indexed db, and websql.

Example

// Picks the best store available.
var db = await Store.open('simple-run-through', 'test');

await db.open();
await db.nuke();
await db.save('world', 'hello');
await db.save('is fun', 'dart');

var value = await db.getByKey('hello');

querySelector('#text').text = value;

See the example/ directory for more sample code.

Choosing the best storage option

This is now made easy for you. Simply create a new instance of Store:

var store = await Store.open('dbName', 'storeName');

The factory constructor will try IndexedDB, then WebSQL, and then finally local storage. Of course, you can perform your own logic to choose which option works for you.

API

Future Store.open() Opens the database and makes it available for reading and writing.

Future nuke() Wipes the database clean. All records are deleted.

Future save(value, key) Stores a value accessible by a key.

Future getByKey(key) Retrieves a value, given a key.

Stream keys() Returns all keys.

Stream all() Returns all values.

Future batch(map) Stores all values and their keys.

Stream getByKeys(keys) Returns all values, given keys.

Future exists(key) Returns true if the key exists, or false.

Future removeByKey(key) Removes the value for the key.

Future removeByKeys(keys) Removes all values for the keys.

Usage

Most methods return a Future, like open and save. Methods that would return many things, like all, return a Stream.

Supported storage mechanisms

• Indexed DB - Great choice for modern browsers
• WebSQL - Well supported in mobile WebKit browsers, not in Firefox
• Local Storage - Only 5MB, slow, more-or-less universal
• Memory - Good for testing

You can consult Can I Use? for a breakdown of browser support for the various storage technologies.

Install

Lawndart is a pub package. To install it, and link it into your app, add lawndart to your pubspec.yaml. For example:

name: your_cool_app
dependencies:
  lawndart: any

If you use Dart Editor, select your project from the Files view, then go to Tools, and run Pub Install.

If you use the command line, ensure the Dart SDK is on your path, and the run: pub install

Support

Lawndart is hosted at https://github.com/sethladd/lawndart

You can file issues at https://github.com/sethladd/lawndart/issues

API docs at http://sethladd.github.com/lawndart/

This library is open source, pull requests welcome!

Authors

• Seth Ladd (sethladd@gmail.com)

License

Copyright 2015 Google

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.