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POAngularJS : Where to use promises?
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  1. POAngularJS : Where to use promises?
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    copied!<p>I saw some examples of Facebook Login services that were using <strong>promises</strong> to access FB Graph API. </p> <p><strong>Example #1</strong>:</p> <pre><code>this.api = function(item) { var deferred = $q.defer(); if (item) { facebook.FB.api('/' + item, function (result) { $rootScope.$apply(function () { if (angular.isUndefined(result.error)) { deferred.resolve(result); } else { deferred.reject(result.error); } }); }); } return deferred.promise; } </code></pre> <p>And services that used <code>"$scope.$digest() // Manual scope evaluation"</code> when got the response </p> <p><strong>Example #2</strong>:</p> <pre><code>angular.module('HomePageModule', []).factory('facebookConnect', function() { return new function() { this.askFacebookForAuthentication = function(fail, success) { FB.login(function(response) { if (response.authResponse) { FB.api('/me', success); } else { fail('User cancelled login or did not fully authorize.'); } }); } } }); function ConnectCtrl(facebookConnect, $scope, $resource) { $scope.user = {} $scope.error = null; $scope.registerWithFacebook = function() { facebookConnect.askFacebookForAuthentication( function(reason) { // fail $scope.error = reason; }, function(user) { // success $scope.user = user $scope.$digest() // Manual scope evaluation }); } } </code></pre> <p><a href="http://jsfiddle.net/mkotsur/Hxbqd/" rel="noreferrer">JSFiddle</a> </p> <p>The questions are: </p> <ul> <li>What is the <strong>difference</strong> in the examples above? </li> <li>What are the <strong>reasons</strong> and <strong>cases</strong> to use <em>$q</em> service?</li> <li>And how does it <strong>work</strong>?</li> </ul>
 

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