如何在AngularJS头模板中动态检查$ rootScope.userDetails？

I would like to have two different headers based on if a user is logged in or not. User Access details are stored in $rootScope.userDetails. The property is deleted from the $rootScope object as soon as I have logged out. The problem is my header file does not recognise the change in object and keeps showing the original header throughout the app.I would like to have two different headers base