How to modify scope from within a directive in AngularJs

Question

I need to modify a root scope attribute from within a callback inside a directive. But the directive is in a inner scope created by a switch directive.

HTML

Answer 1

I updated the fiddle, basically had to go to the parent to get the right "selected" variable, also used the isolate scope = to get two way binding between the value passed in and the internal model.

http://jsfiddle.net/nJ7FQ/2/

angular.module('app', [])

    .directive("customTag", [function () {
    return {
        restrict: "E",
        replace: true,
        template: "<input type='button' value='Click me' />",
        scope: {model:'='},

        link: function (scope, element, attrs) {
            element.bind('click', function () {
                scope.model[attrs.selectedItem] = "New value";
                scope.$apply();
            });
        }
    };
}]);

function AppController($scope) {
    $scope.selected = 'Old value';
}

and the HTML

<div ng-app="app" ng-controller='AppController'>
    <p>Selected: {{ selected }}</p>
    <div ng-switch on="selected">
        <div ng-switch-default>
            <p>Item: {{ selected }}</p>
            <custom-tag selected-item="selected" model="$parent" />
        </div>
        <div ng-switch-when="New value">
            <p>Worked</p>
        </div>
    </div>
</div>

Updated the fiddle to use your original reading of the property from the attribute: http://jsfiddle.net/nJ7FQ/4/

Answer 2

I improved the jsfiddle a bit:

angular.module('app', [])

    .directive("customTag", ['$parse', function ($parse) {
    return {
        restrict: "E",
        replace: true,
        template: "<input type='button' value='Click me' />",

        link: function (scope, element, attrs) {
            element.bind('click', function () {
                scope.$apply(function () {
                    $parse(attrs.selectedItem).assign(scope.$parent, "New value");
                });
            });
        }
    };
}]);

function AppController($scope) {
    $scope.selected = { 'foo': 'Old value' };
}

http://jsfiddle.net/nJ7FQ/15/

This way, the scope value, you want to change can also be an object property like selected.foo in the example. Also, I removed the scope parameter and told the directive to always use the parent scope. And finally I wrapped the click handler into the $apply callback (see here for example). Better would be, of course, to use ngClick instead of the element.bind().