push data from one controller to another, $resource service - angularjs

Question

I'm using angular routing for a SPA with a sidebar (on index.html) that loads a list of categories from a categoryListController, which has a categoryData $resource service injected for retrieving the category list.
Then i have a template, addCategory.html which adds a category with the help of a addCategoryController, which also uses categoryData $resource service.
$scope.categories = categoryData.query(); //categoryListController (for sidebar)
categoryData.save(newCategory) // on addCategoryController (for addCategory.html)
The problem is, the sidebar won't update unless I refresh the entire page. I'm thinking i've got to somehow tell the categoryListController to refresh, but i'm not sure how to do that. I can do $scope.categories.push(newCategory) right after categoryData.save(newCategory), and get the new category showing immediately on addCategory.html, but i don't think that's the answer for my sidebar, unless this is something that needs to be handled with $rootscope? I'm not sure. Thanks

Answer 1

One of the approach that you can take here to update the list of categories in categoryListController would be to use $rootScope to broadcast message detailing the category added.
Catch this message in the list controller to either fetch the list again from server or use the newly added item send using the broadcast message to the list.
Something like this in the Add controller
$rootScope.$broadcast('categoryAdded', { 'category': newcategoryObject });
Something like this in list controller
$scope.$on('categoryAdded', function (event, args) {
$scope.categories.push(args.category);
});
You can inject $rootScope as a dependency into the controller.
You can do a similar thing by creating a CategoryList service too. Since service are singleton by nature and can be shared across controllers, using the service approach you would define a CategoryList service with methods to get and `add' categories and bind to data returned by this service.

Answer 2

You should create a service that share the data structure and care of managing the content.
Something like this:
angular.service('categoryService', function() {
var categories = [], initilized;
return {
this.getCategories = function() {
if (!initialized) {
// call resource to fulfill the categories array
initialized = true;
}
// you cold return a promise that would be resolved as soon
// as you get the first response from server
return categories;
});
this.addCategory = function(category) {
// code to call $resource, add the category and update the
// categories array, shared between both controllers
//
// you could return the promise for adding the content
});
this.removeCategory = ...
};
});
 
You wouldn't need to even call $resource, this service would care of any need of persisting. Of course, you might change and add more method if you need to expose the promises.