A plugin to make Backbone.js keep track of nested attributes.
Filed under application tools › utilities

Backbone-Nested

A plugin to make Backbone.js keep track of nested attributes. Download the latest version and see the changelog/history/release notes on the Releases page. Supports Backbone 0.9.x and 1.x.

The Need

Suppose you have a Backbone Model with nested attributes, perhaps to remain consistent with your document-oriented database. Updating the nested attribute won't cause the model's "change" event to fire, which is confusing.

var user = new Backbone.Model({
  name: {
    first: 'Aidan',
    last: 'Feldman'
  }
});

user.bind('change', function(){
  // this is never reached!
});

user.get('name').first = 'Bob';
user.save();

Wouldn't it be awesome if you could do this?

user.bind('change:name.first', function(){ ... });

Installation

Bower

Recommended.

Install the latest version:

 bower install backbone backbone-nested-model jquery underscore --save

Add backbone-nested.js to your HTML <head>:

 <!-- must loaded in this order -->
 <script type="text/javascript" src="/bower_components/jquery/jquery.js"></script>
 <script type="text/javascript" src="/bower_components/underscore/underscore.js"></script>
 <script type="text/javascript" src="/bower_components/backbone/backbone.js"></script>
 <script type="text/javascript" src="/bower_components/backbone-nested-model/backbone-nested.js"></script>

Manual

Download the latest release and the dependencies listed above, then include with script tags in your HTML.

Usage

Change your models to extend from Backbone.NestedModel, e.g.

 var Person = Backbone.Model.extend({ ... });

 // becomes

 var Person = Backbone.NestedModel.extend({ ... });

Change your getters and setters to not access nested attributes directly, e.g.

 user.get('name').first = 'Bob';

 // becomes

 user.set({'name.first': 'Bob'});

Best of all, Backbone.NestedModel is designed to be a backwards-compatible, drop-in replacement of Backbone.Model, so the switch can be made painlessly.

Nested Attributes

get() and set() will work as before, but nested attributes should be accessed using the Backbone-Nested string syntax:

1-1

// dot syntax
user.set({
  'name.first': 'Bob',
  'name.middle.initial': 'H'
});
user.get('name.first') // returns 'Bob'
user.get('name.middle.initial') // returns 'H'

// object syntax
user.set({
  'name': {
    first: 'Barack',
    last: 'Obama'
  }
});

1-N

// object syntax
user.set({
  'addresses': [
    {city: 'Brooklyn', state: 'NY'},
    {city: 'Oak Park', state: 'IL'}
  ]
});
user.get('addresses[0].state') // returns 'NY'

// square bracket syntax
user.set({
  'addresses[1].state': 'MI'
});

Events

"change"

"change" events can be bound to nested attributes in the same way, and changing nested attributes will fire up the chain:

// all of these will fire when 'name.middle.initial' is set or changed
user.bind('change', function(model, newVal){ ... });
user.bind('change:name', function(model, newName){ ... });
user.bind('change:name.middle', function(model, newMiddleName){ ... });
user.bind('change:name.middle.initial', function(model, newInitial){ ... });

// all of these will fire when the first address is added or changed
user.bind('change', function(model, newVal){ ... });
user.bind('change:addresses', function(model, addrs){ ... });
user.bind('change:addresses[0]', function(model, newAddr){ ... });
user.bind('change:addresses[0].city', function(model, newCity){ ... });

"add" and "remove"

Additionally, nested arrays fire "add" and "remove" events:

user.bind('add:addresses', function(model, newAddr){ ... });
user.bind('remove:addresses', function(model, oldAddr){ ... });

Special Methods

add()

Acts like set(), but appends the item to the nested array. For example:

user.get('addresses').length; //=> 2
user.add('addresses', {
  city: 'Seattle',
  state: 'WA'
});
user.get('addresses').length; //=> 3

remove()

Acts like unset(), but if the unset item is an element in a nested array, the array will be compacted. For example:

user.get('addresses').length; //=> 2
user.remove('addresses[0]');
user.get('addresses').length; //=> 1

Contributing

Pull requests are more than welcome - please add tests, which can be run by opening test/index.html. They can also be run from the command-line (requires PhantomJS):

$ npm install
$ grunt

See also: live tests for latest release.

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