How modify objects across scopes in AngularJS?

I am new to AngularJS, the notion of scopes really confuses me. I have a situation where I want to modify a an object or a variable from different scopes. Here is why: in my application I want to centralize the user notification Controller and notification view. In the middle top of the page. I separate my code as follow: each view has its controller I think its fair reasonable. I want to inject a service or some common object that when invoking its function with some string parameter on a common place but, I figured out that I can not inject $scope service. So, when

What you want is to communicate between controllers. That is fairly easy to realize whit a service that can broadcast messages (or objects) between controllers.

There is a nice youtube about this:

http://www.youtube.com/watch?v=1OALSkJGsRw

OK here what I have done in my application. I am a java programmer and I used to work with GWT

In GWT ther is a very nice design pattern, to notify widgets across the application, called EventBus. In angular I tried to do something similar. Here is the code link in gist