Lightweight Relation Modeling with Backbone (5)

gistfile1.js

function delegateModelEvents(from, to, eventKey) {
    from.bind('all', function(eventName) {
        var args = _.toArray(arguments);
        if (eventKey) {
            args[0] = eventKey + ':' + args[0];
        }
        to.trigger.apply(to, args);
    });
}

function getUpdateOp(model) {
    return (model instanceof Backbone.Collection) ? 'reset' : 'set';
}

Backbone.RelationalModel = Backbone.Model.extend({
    relations: {},
    set: function(attrs, options) {
        _.each(this.relations, function(constructor, key) {
            var relation = this[key];

            // set up relational model if it's not there yet
            if (!relation) {
                relation = this[key] = new constructor();

                // makes it so relation events are triggered out
                // e.g. 'add' on a relation called 'collection' would
                // trigger event 'collection:add' on this model
                delegateModelEvents(relation, this, key);
            }

            // check to see if incoming set will affect relation
            if (attrs[key]) {
                // perform update on relation model
                relation[getUpdateOp(relation)](attrs[key], options);

                // remove from attr hash, prevents duplication of data +
                // keeps models out of attributes, which should be only used for
                // dumb JSON attributes
                delete attrs[key];
            }
        }, this);

        return Backbone.Model.prototype.set.call(this, attrs, options);
    }
});​