How to modify scope from within a directive in AngularJs - 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
<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" />
</div>
<div ng-switch-when="New value">
<p>Worked</p>
</div>
</div>
</div>
JavaScript
angular.module('app', [])
.directive("customTag", [function () {
return {
restrict: "E",
replace: true,
template: "<input type='button' value='Click me' />",
link: function (scope, element, attrs) {
element.bind('click', function () {
scope[attrs.selectedItem] = "New value";
scope.$apply();
});
}
};
}]);
function AppController($scope) {
$scope.selected = 'Old value';
}
Fiddle: http://jsfiddle.net/nJ7FQ/
My objective is to be able to display "New value" in the Selected area.
How can I accomplish what I am trying to do? What am I doing wrong?
Besides, as I am trying to make a component. Is there a way to do the same but with an isolated scope?

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().