Promise and Deferred in AngularJS

Reference

Very simple example of using promises
http://markdalgleish.com/2013/06/using-promises-in-angularjs-views/

An example of using notify() to update progress
http://nurkiewicz.blogspot.com/2013/03/promises-and-deferred-objects-in-jquery.html

Official document of AngularJS promise/deferred
http://docs.angularjs.org/api/ng.$q

compare code : callback .vs. promise

Callback	Promise
in function var getMessages = function(callback) {     $timeout(function() {         callback(['Hello', 'World!']);     }, 2000); }	in function var getMessages = function() {     var deferred = $q.defer();     $timeout(function() {         deferred.resolve(['Hello', 'World!']);     }, 2000);     return deferred.promise; }
in controller getMessages(function(messages) {     $scope.messages = messages; });	in controller getMessages().then(function(messages) {     $scope.messages = messages; });

promise with notify()

in function
var getMessages = function() {
    var deferred = $q.defer();

    var id = setInterval(function() {
        deferred.notify();
    }, 1000);

    $timeout(function() {
        clearInterval(id);
        deferred.resolve(['Hello', 'World!']);
    }, 9000);
    return deferred.promise;
}


in controller
HelloWorldP.getMessages().then(
function(messages) { // function for resolve() callback
    $scope.p.messagesp = messages;
}, 
null, // function for error callback
function(){// function for notify() callback
    $scope.p.waiting_msg += '.';
});