Promises and Syncing the View and Model in Angular - angularjs

Question

My basic question is what is the best practice for keeping the model and the view in synch in angular, especially when it is a single object. I have been trying to play around with promises, but cant seem to get anything to work. The thing I am trying to do is increment the upvotes on post, a popular example.
ok heres the code: function I am working on is the incrementUpvotes function.
Factory:
(function() {
ngNewsApp.factory('posts', posts);
posts.$inject = ['$http', '$q'];
function posts($http, $q) {
var service = {
postList: [],
getPosts: function() {
return $http.get('/posts').success(function(data) {
angular.copy(data, service.postList);
});
},
savePost: function(post) {
return $http.post('/posts', post).success(function(data) {
service.postList.push(data);
});
},
getPost: function(id) {
return $http.post('/posts/' + id).success(function(result) {
return result.data;
});
},
upvote: function(post) {
return $http.put('/posts/' + post._id + '/upvote');
}
};
return service;
}
})();
Controller:
ngNewsApp
.controller('MainCtrl', ['$scope', 'posts', function ($scope, posts) {
$scope.posts = posts.postList;
$scope.addPost = function() {
if(!$scope.title || $scope.title === '') {
return;
}
posts.savePost({
title: $scope.title,
link: $scope.link
});
$scope.title = '';
$scope.link = '';
};
$scope.incrementUpvotes = function(post) {
posts.upvote(post).success(function(post) {
post.upvotes++;
});
};
}]);