AngularJS ModelService paradigm for sharing data between controllers

app.js

// Quick and dirty example that illustrates the ModelService paradigm
// for sharing data models between multiple controllers.
//
// Once `UserService` is injected into a controller and `UserService.login()` 
// returns successfully, any expressions data-bound to properties of the
// `UserService.model` object in the scope of other controllers should be properly updated.
//
// In this example, model mutation is controlled within the context of the
// service, so only calls to `UserService.login()` will update `UserService.model`.
// It would also make since to have the UserService API expose an `update()`
// function that wraps $ngResource and updates the data model accordingly.

// http-auth-interceptor - https://github.com/witoldsz/angular-http-auth
// is used to implement basic authentication.
angular.module('TestApp', ['ngResource', 'http-auth-interceptor'])

// I prefer using PUT's to update backend collections, so
// $save is overwritten to call create() or update() as needed
.factory('Resource', function ($resource) {
  return function (url, params, methods) {
    var defaults = {
      create: { method: 'post' },
      update: { method: 'put' }
    };

    methods = angular.extend(defaults, methods);

    var resource = $resource(url, params, methods);

    resource.prototype.$save = function() {
      if (!this._id) {
        return this.$create();
      } else {
        return this.$update();
      }   
    };  

    return resource;
  };  
})

// Simple UserService which exposes an API that wraps RESTful routes
// and allows model data to be shared between controllers
.service('UserService', function (Resource, authService) {
  var URL = 'http://api.example.com/';
  var UserModel = { email: '', password: '', fullName: '', age: '' };

  // UserResource will now contain get(), save(), query(), delete(),
  // signup(), login(), and logout() methods. 
  var UserResource = Resource(URL + 'user/:id', { id: '@_id' }, {
    signup: { method: 'post', url: URL + 'signup' },
    login: { method: 'post', url: URL + 'login', withCredentials: true, ignoreAuthModule: true },
    logout: { method: 'post', url: URL + 'logout', withCredentials: true }
  }); 

  // UserService contains our desired API
  var UserService = { 
    // Expose User data model
    model: UserModel,

    // Custom login implementation since we're using
    // http-auth-interceptor module
    login: function (user, success, failure) {
      UserResource.login(user, function(data) {
        UserModel = user;
        authService.loginConfirmed();
        if (success) success(data);
      }, function(error) {
        if (failure) failure(error);
      }); 
    },  

    // delegates to ngResource
    logout: UserResource.logout,

    // delegates to ngResource
    signup: UserResource.signup
  };  

  // Expose the service API
  // If we wanted all of the UserResource methods it would make sense
  // to `return angular.extend(UserResource, UserService)` instead
  return UserService;
});