Data Service Factory using $q

data.service.js

/**
 * dataservice Factory
 * @namespace Factories
 * @author Wandrille Verlut <wandrille.verlut@gmail.com>
 */

(function() {
    'use strict';
    angular
        .module('app')
        .factory('dataservice', dataservice);

    dataservice.$inject = ['$http', '$q', 'ELEMENTS_LIST', 'BACKEND_URL'];

    /**
     * @namespace dataservice
     * @desc Manage backend queries
     * @memberOf Factories
     */
    function dataservice($http, $q, ELEMENTS_LIST, BACKEND_URL) {
        return {
            getSitesStatus : getSitesStatus
        };

        /////

        /**
         * @name getElementsInfos
         * @desc Retrieve elements infos from a backend
         * @return {Array} a list of elements with their infos
         */
        function getElementsInfos() {
            var elements = ELEMENTS_LIST;
            var countDown = elements.length; // indicates when async calls are done
            var deferred = $q.defer(); //creates a promise manager

            elements.forEach(function(e) {

                // For each element, we ask Backend for infos
                $http.get(BACKEND_URL + e.id)
                    .then(function onBackendResolve(response) {

                            /** @todo : treat data */
                            e.infos = response.data;
                            
                            // if all asyncrhonous calls are done, solve the promise and return the sites
                            countDown -= 1;
                            if (countDown === 0) {deferred.resolve(elements);} 
                        }
                    })
                    .catch(function onBackendError(response) {
                        
                        /** @todo : treat anomaly */
                        e.infos = 'error';

                        countDown -= 1;
                        if (countDown === 0) {deferred.resolve(elements);}
                    });
            });
            return deferred.promise;
        }
    }

})();