Angular ui-router: how to prevent access to a state

Hello I'm new to angularJS and have been trying to prevent access to certain states based on user critera.

This, from ui-router's FAQ describes exactly what I want to do, but I cant get it to work properly. What do I need to but in the data object exactly to accomplish this?

(I saw someone throwing in "true" on some blog post tutorial and using it like how I have, but that doesnt seem to work because I get an error that says needAdmin is not defined)

Here is my code:

angular.module('courses').config(['$stateProvider',
    function($stateProvider) {
        // Courses state routing
        $stateProvider.
        state('listCourses', {
            url: '/courses',
            templateUrl: 'modules/courses/views/list-courses.client.view.html'
        }).
        state('createCourse', {
            url: '/courses/create',
            templateUrl: 'modules/courses/views/create-course.client.view.html',
            data: {
                needAdmin: true
            }
        }).
        state('viewCourse', {
            url: '/courses/:courseId',
            templateUrl: 'modules/courses/views/view-course.client.view.html'
        }).
        state('editCourse', {
            url: '/courses/:courseId/edit',
            templateUrl: 'modules/courses/views/edit-course.client.view.html',
            data: {
                needAdmin: true
            }
        });     

    }
]);


angular.module('courses').run(['$rootScope', '$state', 'Authentication', function($rootScope, $state, Authentication) {
  $rootScope.$on('$stateChangeStart', function(e, to) {

    var auth = Authentication;

    console.log(auth.user.roles[0]);
    if (to.data.needAdmin && auth.user.roles[0] !== 'admin') {
      e.preventDefault();
      $state.go('/courses');
    }

  });
}]);