Backbone Model Composite

This library is a small extension to the basic Backbone Model class, which supports nested models.

Install

As a Node package

npm install backbone-model-composite

With Bower

bower install backbone-model-composite

Use

Child models

Define child models using a childModels hash.

var ParentModel = Backbone.ModelComposite.extend({
  childModels: {
    firstChild: Backbone.Model,
    secondChild: OtherConstructor
  }

  //...
});

Attributes passed to the parent model's constructor, with keys from childModels are used to instantiate its child models.

var model = new ParentModel({
  firstChild: {
    a: 'abc',
    b: 2
  },
  secondChild: {},
  x: 3
});

model.firstChild.get('a'); // <-- 'abc'
model.secondChild.set('hello', 'world');

By default, attributes used to create child models are removed from the parent object. Pass preserveChildAttributes in the constructor's options hash to keep these attributes on the parent.

toJson()

Backbone.Model's toJSON() method is overriden to include the nested models. Pass excludeChildModels in an options hash to prevent this behavior.

model.toJSON(); // <-- {firstChild: {a: 'abc', b: 2}, secondChild: {hello: 'world'}, x: 3}    
model.toJSON({excludeChildModels: true}); // <-- {x: 3}

Nesting

Multiple levels of nesting are supported:

var SecondaryModel = Backbone.ModelComposite.extend({
  childModels: {
    tertiary: Backbone.Model
  }
});

var TopModel = Backbone.ModelComposite.extend({
  childModels: {
    secondary: SecondaryModel 
  }
});

var model = new TopModel({first: 1});
model.secondary.set("second", 2);
model.secondary.tertiary.set("third", 3);

model.toJSON(); // <-- {first: 1, secondary: {second: 2, tertiary: {third :3}}}

Event propagation

The parent object also emits its children's events, prefixed with the key from the childModels hash.

var model = new ParentModel();
var handler = function (){};
model.on('firstChild:change', handler);
model.firstChild.set('a', 123); // handler called