Creating a scope-independent fadein/fadeout directive in AngularJS - angularjs

Question

To set the stage - this is not happening within a single scope, where I can bind a simple attribute. The element I want to fade in/out does not sit inside a controller, it sits inside the ng-app (rootScope). Further, the button that's clicked is in a child scope about 3 children deep from root.
Here is how I'm currently solving this:
HTML (sitting in root scope):
<ul class="nav-secondary actions"
darthFader fadeDuration="200"
fadeEvent="darthFader:secondaryNav">
Where darthFader is my directive.
Directive:
directive('darthFader',
function() {
return {
restrict: 'A',
link: function($scope, element, attrs) {
$scope.$on(attrs.fadeevent, function(event,options) {
$(element)["fade" + options.fade || "In"](attrs.fadeduration || 200);
});
}
}
})
So here I'm creating an event handler, specific to a given element, that is calling fadeIn or fadeOut, depending on an option being passed through the event bus (or defaulting to fadeIn/200ms).
I am then broadcasting an event from $rootScope to trigger this event:
$rootScope.$broadcast('darthFader:secondaryNav', { fade: "Out"});
While this works, I'm not crazy about creating an event listener for every instance of this directive (while I don't anticipate having too many darthFader's on a screen, it's more for the pattern I would establish). I'm also not crazy about coupling my attribute in my view with an event handler in both my controller & directive, but I don't currently have a controller wrapping the secondary-nav, so I'd have to bind the secondaryNav to $rootScope, which I don't love either. So my questions:
Is there a way to do this without creating an event handler every time I instantiate my directive? (maybe a service to store a stateful list of elements?)
How should I decouple my view, controller & directive?
Any other obvious questions I'm missing?
Cheers!

Answer 1

You mention in your question
The element I want to fade in/out does not sit inside a controller, it sits inside the ng-app (rootScope).
I believe if I were to write this same functionality, I would put the element in its own controller--controllers are responsible for managing the intersection of the view and the model, which is exactly what you're trying to do.
myApp.controller('NavController', function($scope) {
$scope.fadedIn = false;
});
<ul ng-controller="NavController"
class="nav-secondary actions"
darthFader fadeDuration="200"
fadeShown="fadedIn">
myApp.directive('darthFader', function() {
return {
restrict: 'A',
link: function($scope, element, attrs) {
var duration = attrs.fadeDuration || 200;
$scope.$watch(attrs.fadeShown, function(value) {
if (value)
$(element).fadeIn(duration);
else
$(element).fadeOut(duration);
});
}
};
});
If you're worried about sharing the fade in/out state between multiple controllers, you should create a service to share this state. (You could also use $rootScope and event handlers, but I generally find shared services easier to debug and test.)
myApp.value('NavigationState', {
shown: false
});
myApp.controller('NavController', function($scope, NavigationState) {
$scope.nav = NavigationState;
});
myApp.controller('OtherController', function($scope, NavigationState) {
$scope.showNav = function() {
NavigationState.shown = true;
};
$scope.hideNav = function() {
NavigationState.shown = false;
};
});
<ul ng-controller="NavController"
class="nav-secondary actions"
darthFader fadeDuration="200"
fadeShown="nav.shown">
<!-- ..... -->
<div ng-controller="OtherController">
<button ng-click="showNav()">Show Nav</button>
<button ng-click="hideNav()">Hide Nav</button>
</div>

Answer 2

Create a custom service, inject it in the controller. Call a method on that service that will do the fade-in/fade-out etc. Pass a parameter to convey additional information.