Unable to use angular factory cross routes - angularjs

Question

I'm trying to create a factory and use it cross routes in each controller but apparently I'm doing something wrong...
The app:
var app = angular.module('sam', ['ngRoute', 'ngGrid', 'ui.bootstrap']);
The factory
app.factory("User",function(){
return {};
});
The routes
// configure our routes
app.config(function($routeProvider) {
$routeProvider
// route for the main page which will direct to the buildings page
.when('/', {
templateUrl : 'web/pages/buildings.html',
controller : 'mainController',
controllerAs : 'buildings'
})
});
The controller
app.controller('mainController', ['$filter', '$http','$log', function($filter, $http, $log, User){
$log.log('hello!!!!!', User);
}]);
This prints : hello!!!!! undefined

Answer 1

you are missing 'User' in your controller.
app.controller('mainController', ['$filter', '$http','$log', **'User',** function($filter, $http, $log, User){
$log.log('hello!!!!!', User);
}]);

Answer 2

You forgot to include User as part of injection array
controller('mainController', ['$filter', '$http','$log', function($filter, $http, $log, User){
Should be:
controller('mainController', ['$filter', '$http','$log','User', function($filter, $http, $log, User){

Answer 3

app.factory("User",function(){
return {
show:function(){
alert('Factory called')
}
};
});
app.controller('mainController', ['$filter', '$http','$log','User', function($filter, $http, $log, User){
//that is the way you can call your factory
// you can call this factory function in any controller by injecting it.
User.show(); //will popup alert window.
}]);