title: Multiple usages of same controller in angular
body: <p>problem with angular. On my website a have comments. Each comment shares the same 'ng-controller="commentCtrl"' directive. Now when I have about 300 comments on my web site, there are 300 commentCtrl instances. In the html of the controller I am using ng-disabled="author_provided()" on a button.
  When I am changing the author input text field, all the 300 comments are invoking author_provided() ( because this function depends on on the author ng-model). This causes performance issues. I want the author_provided() function be invoked only in the controller where I am changing the author. How to achieve that ?</p>