AngularJS : factory $http service

Question

I am trying to understand the concept of factory and service in Angular. I have the following code under the controller

init();

    function init(){
        $http.post('/services', { 
            type : 'getSource',
            ID    : 'TP001'
        }).
        success(function(data, status) {
            updateData(data);
        }).
        error(function(data, status) {

        });

        console.log(contentVariable);
    };
    function updateData(data){
        console.log(data);
    };

This code works fine. But when i move $http service into factory, i am not able to return data back to controller.

studentApp.factory('studentSessionFactory', function($http){
    var factory = {};
    factory.getSessions = function(){
        $http.post('/services', { 
            type : 'getSource',
            ID    : 'TP001'
        }).
        success(function(data, status) {
            return data;
        }).
        error(function(data, status) {

        });
    };
    return factory;
});

studentApp.controller('studentMenu',function($scope, studentSessionFactory){
    $scope.variableName = [];
    init();
    function init(){
        $scope.variableName = studentSessionFactory.getSessions();
        console.log($scope.variableName);
    };
});

Is there any advantage to using factory, since $http works even under controller

Answer 1

The first answer is great but maybe you can understand this:

studentApp.factory('studentSessionFactory', function($http){
    var factory = {};

    factory.getSessions = function(){
        return $http.post('/services', {type :'getSource',ID :'TP001'});
    };

    return factory;
});

Then:

studentApp.controller('studentMenu',function($scope, studentSessionFactory){
      $scope.variableName = [];

      init();

      function init(){
          studentSessionFactory.getSessions().success(function(data, status){
              $scope.variableName = data;
          });
          console.log($scope.variableName);
     };
 });

Answer 2

The purpose of moving your studentSessions service out of your controller is to achieve separation of concerns. Your service's job is to know how to talk with the server and the controller's job is to translate between view data and server data.

But you are confusing your asynchronous handlers and what is returning what. The controller still needs to tell the service what to do when the data is received later...

studentApp.factory('studentSession', function($http){
    return {
        getSessions: function() {
            return $http.post('/services', { 
                type : 'getSource',
                ID    : 'TP001'
            });
        }
    };
});

studentApp.controller('studentMenu',function($scope, studentSession){
    $scope.variableName = [];

    var handleSuccess = function(data, status) {
        $scope.variableName = data;
        console.log($scope.variableName);
    };

    studentSession.getSessions().success(handleSuccess);
});