AngularJS directive with function (no arguments)

directive.js

myApp.directive('callbackDirective', function () {
    return {
        scope: {
            callback: '&'            
        },
        restrict: 'E',
         templateUrl: 'my-template.html'
        controller: ['$scope', function ($scope) {
            $scope.foo = function () {
                if ($scope.callback) {
                    $scope.callback();
                }
            };
        }]
    }
})

page.html

<callback-directive callback="myCallback()" />