AngularJS PubSub Engine

gistfile1.js

/*global _:false */

'use strict';

angular.module('PubSubEngineModule')
    .factory('PubSubEngine', ['$q', '$rootScope',
        function($q, $rootScope) {

            var PubSubEngine = {};

            /** raise an event with a given name, returns an array of promises for each listener */
            PubSubEngine.publish = function(name, args) {

                //there are no listeners
                if (!$rootScope.$$listeners[name]) {
                    return [];
                }

                //setup a deferred promise for each listener
                var deferred = [],
                    i = 0,
                    len = $rootScope.$$listeners[name].length;
                for (i; i < len; i++) {
                    deferred.push($q.defer());
                }
                //create a new event args object to pass to the
                // $broadcast containing methods that will allow listeners
                // to return data in an async if required
                var eventArgs = {
                    args: args,
                    reject: function(a) {
                        deferred.pop().reject(a);
                    },
                    resolve: function(a) {
                        deferred.pop().resolve(a);
                    }
                };

                //send the event
                $rootScope.$broadcast(name, eventArgs);

                //return an array of promises
                var promises = _.map(deferred, function(p) {
                    return p.promise;
                });
                return promises;
            };

            /** subscribe to a method, or use scope.$on = same thing */
            PubSubEngine.subscribe = function(name, callback) {
                return $rootScope.$on(name, callback);
            };

            /** pass in the result of subscribe to this method, or just call the method returned from subscribe to unsubscribe */
            PubSubEngine.unsubscribe = function(handle) {
                if (angular.isFunction(handle)) {
                    handle();
                }
            };

            return PubSubEngine;

        }
    ]);