ng-hide from parent scope

How to take the ng-bind value and apply to the isolated scope.

HTML

<script src="http://code.angularjs.org/1.0.0rc6/angular-1.0.0rc6.min.js"></script>
<html ng-app="app">
<body ng-controller="Ctrl">
    directive 1: <span ng-hide='hide' dir1='desc' dir2='desc'></span><br>
    directive 2: <span ng-hide='hide' ></span><br>
    <input type='checkbox' ng-model='hide'> HIDE
</body>
</html>

JavaScript

function Main() {}

angular.module('app', []).directive('dir1', function() {
    return {
        restrict: 'A',
        scope: {
            dir1: 'evaluate',
            ngHide: 'accessor'
        },
        link: function(scope, elm, attr, ngModelCtrl) {
            this.element = elm;
            element.text(scope.dir1);

            // Bind from parent.
            scope.$watch(function() {
                return scope.ngHide()
            }, function(value) {
                element.css('display', value ? 'none' : '');
                scope.hideElem = value;
            });
        }
    };
}).directive('dir2', function() {
    return {
        restrict: 'A',
        link: function(scope, elm, attr, ngModelCtrl) {
            elm.text(scope.$eval(attr.dir2));
        }
    };
});

function Ctrl($scope) {
    $scope.desc = 'popis'
}