requireajax.js

var apiRelationalCollection = {
    method: false,
    type: false,
    loading: function (data) {
        return data;
    },
    data: false,
    relational: false
};

var apiRelationalModel = {
    method: false,
    type: false,
    loading: function (data) {
        return data;
    },
    data: false,
    relational: false
};

var createItem = function (item, callback) {
    var url = item.type + '/' + item.group + '/' + item.name;
    var Class = this.app[item.type][item.name];

    require([url], function (Func) {

        Class = new Func();
        return callback(Class);

    });
};


apiRelationalInitModel = function () {

    var that = this;

};

apiRelationalInitCollection = function (data, success, error, relationals) {

    var that = this;

    if (!this.apiRelational) {
        return success(this);
    }

    var setData = function (resp) {
        this.reset(this.apiRelational.loading.apply(resp));
    };

    var itemAjaxMethod = function (callback) {

        var that = this;

        if (!this.apiRelational || !this.apiRelational.method) {
            callback();
        }

        var method = that.app.api[that.apiRelational.method];

        if (!method) {
            callback();
        }

        data = _.extend({}, this.apiRelational.data);

        if (method) {
            method(data, function (resp) {
                setData.call(that, resp);
                callback();
            });
        } else {
            callback();
        }


    };

    var createItem = function (item, callback) {
        var that = this;

        var url = item.type + '/' + item.group + '/' + item.name;
        var Class = this.app[item.type][item.name];

        if (Class) {
            return callback(Class);
        }

        require([url], function (Func) {

            Class = new Func();
            that.app[item.type][item.name] = Class;

            Class.apiRelationalInit({}, function (resp) {

                return callback(Class);

            }, function (resp) {
                // console.log('createCollection false', resp);
            });


        });
    };

    var createObjItems = function (items, out, callback) {


        if (items.length > 0) {

            var item = items.pop();
            var Class = this.app[item.type][item.name];

            if (Class !== undefined) {
                return createObjItems.call(that, items, out, callback);
            }

            createItem.call(that, item, function (itemClass) {

                out.push(itemClass);
                return createObjItems.call(that, items, out, callback);

            });

        } else {

            callback(out);
        }

    };


    if (this.apiRelational.relational) {

        var items = this.apiRelational.relational;

        if (relationals) {
            items = items.concat(relationals);
        }

        createObjItems.call(that, items, [], function (createditems) {

            itemAjaxMethod.call(that, function () {
                success();
            });

        });


    } else {
        success();
    }

};


Backbone.Model.prototype.apiRelational = apiRelationalModel;
Backbone.Collection.prototype.apiRelational = apiRelationalCollection;
Backbone.Model.prototype.apiRelationalInit = apiRelationalInitModel;
Backbone.Collection.prototype.apiRelationalInit = apiRelationalInitCollection;


/**
 * demo collection
 */

define([
    'jquery',
    'underscore',
    'backbone',
    'models/garage/list_item'
], function ($, _, Backbone, ItemModel) {

    var CarsListCollection = Backbone.Collection.extend({
        model: ItemModel,
        name: 'Cars',

        apiRelational: {
            method: 'getCars',
            loading: function () {
                return this.cars;
            },
            data: {},
            relational: []
        },

        initialize: function () {
            this.app.collections.Cars = this;
        }
    });

    return CarsListCollection;

});

/**
 * in view
 */

this.collection = listCollection;
this.collection.bind('reset', this.renderCollection, this);

this.collection.apiRelationalInit({}, function (resp) {

    // trigger collection.reset here so - this position - render collection

}, function (resp) {
    // console.log('createCollection false', resp);
});