Lazily load associated models and collections from a model easily.

Backbone LazyModel

(function(Factory) {

  if(typeof define !== 'undefined') {

		define(['backbone', 'underscore'], Factory);

	} else if(typeof Backbone !== 'undefined' 
		&& typeof _ !== 'undefined' 
		&& typeof jQuery !== 'undefined') {

		Factory(Backbone, _);
		
	} else {
		throw new Error("LazyModel dependencies not found");
	}

} (function(Backbone, _) {
	Backbone.LazyModel = Backbone.Model.extend({
		_associations: {},

		initialize: function() {			
			_.each(Object.getPrototypeOf(this).relations, 
				function(Model, relation) {
					var _this = this, InnerModel;

					InnterModel = Model.extend({
						initialize: function() {
							this.parent = _this;
						}
					});

					this.setAssoc(relation, InnterModel);
				}, 
				this
			);
		},

		getAssoc: function(name) {
			var assocs = []
			  , _this  = this;

			_.each(arguments, function(arg) {
				assocs.push(this.get('assoc.' + arg));
			}, this);

			return {
				lazyLoad: function(callback) {
					var ready = 0;

					_.each(assocs, function(assoc) {

						if((assoc.attributes && assoc.attributes.length > 0) || 
							(assoc.models && assoc.models.length) ) {

							ready++;
							if(ready === assocs.length) {
								callback.apply(_this, assocs);
							}

						} else {

							assoc.fetch({
								success: function() {
									ready++;
									if(ready === assocs.length) {
										callback.apply(_this, assocs);
									}
								}
							});

						}

					});
				},

				lazyRender: function() {
					var Views = arguments;

					this.lazyLoad(function() {

						_.each(arguments, function(model, match) {
							var view = new Views[match]();

							view.render(model);
						});

					});
				},

				assocs: assocs
			};
		},

		setAssoc: function(name, Model) {
			var model = new Model();

			return this.set('assoc.' + name, model);
		}
	});

	return Backbone.LazyModel;

}));