A dual (localStorage and REST) sync adapter for Backbone.js
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README.md
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README.md

Backbone dualStorage Adapter v1.0

A dualStorage adapter for Backbone. It's a drop-in replacement for Backbone.Sync() to handle saving to a localStorage database as a cache for the remote models.

Usage

Include Backbone.dualStorage after having included Backbone.js:

<script type="text/javascript" src="backbone.js"></script>
<script type="text/javascript" src="backbone.dualstorage.js"></script>

Create your models and collections in the usual way. Feel free to use Backbone as you usually would, this is a drop-in replacement.

Keep in mind that Backbone.dualStorage really loves your models. By default it will cache everything that passes through Backbone.sync. You can override this behaviour with the booleans remote or local on models and collections:

SomeCollection = Backbone.Collection.extend({
    local: true  // always fetched and saved only locally, never saves on remote
    remote: true // never cached, dualStorage is bypassed entirely
});

You can also deactivate dualsync to some requests, when you want to sync with the server only later.

SomeCollection.create({name: "someone"}, {remote: false});

Data synchronization

When the client goes offline, dualStorage allows you to keep changing and destroying records. All changes will be send when the client goes online again.

// server online. Go!
People.fetch();       // load cars models and save them into localstorage

// server offline!
People.create({name: "Turing"});   // you still can create new cars...
People.models[0].save({age: 41});  // update existing ones...
People.models[1].destroy();        // and destroy as well

// server online again!
People.syncDirtyAndDestroyed();    // all changes are sent to the server and localStorage is updated

Keep in mind that if you try to fetch() a collection that has dirty data, only data currently in the localStorage will be loaded. collection.syncDirtyAndDestroyed() needs to be executed before trying to download new data from the server.

Data parsing

Sometimes you may want to customize how data from the remote server is parsed before it's saved to localStorage. Typically your model's parse method takes care of this. Since dualStorage provides two layers of backend, we need a second parse method. For example, if your remote API returns data in a way that the default parse method interprets the result as a single record, use parseBeforeLocalSave to break up the data into an array of records like you would with parse.

  • The model's parse method still parses data read from localStorage.
  • The model's parseBeforeLocalSave method parses data read from the remote before it is saved to localStorage on read.

Credits

Thanks to Jerome Gravel-Niquet for Backbone.dualStorage