ComputedProperty doesn't get updated - ember.js

Question

I have this test application which should print "filtered" and "changed" each time the applications view is clicked, because a computed property is called. However the property binding is only triggered when updating the property with an empty array:
window.App = Ember.Application.create({
Settings: Ember.Object.create({
filter: []
}),
ApplicationView: Ember.View.extend({
click: function(event) {
filter = App.get('Settings.filter');
console.dir(filter);
if (App.get('Room.filtered')) {
filter = filter.filter(function(item) {
return item != App.get('Room.name');
});
} else {
filter.push(App.get('Room.name'));
}
App.set('Settings.filter', filter);
}
})
});
Room = Ember.Object.extend({
name: "test",
_filterer: function() {
console.dir("changed");
}.observes('filtered'),
filtered: function() {
console.dir("filtered");
filter = App.get('Settings.filter');
for (var i = 0; i < filter.length; i++) {
if (filter[i] == this.get('name')) return true;
}
return false;
}.property('App.Settings.filter', 'name').volatile()
});
App.Room = Room.create();
setTimeout(function() {App.set('Settings.filter', ['test']); }, 3000);
Here is the jsbin: http://jsbin.com/edolol/2/edit
Why is the property binding only triggered when setting the Setting to an empty array? And why does it trigger when doing it manually in the timeout?
Update
Here is a working jsbin: http://jsbin.com/edolol/11/edit

Answer 1

When you're going to add/remove items from an array, and not change the entire array, you need to inform the computed property to observe the items inside the array, not only the array itself:
The syntax is:
function() {
}.property('App.settings.filter.#each')
The reason it was working with setTimeout is because you were replacing the entire array instead of the items inside it.
I fixed your jsbin: http://jsbin.com/edolol/10/edit
I fixed some minor other stuff such as filter.push is now filter.pushObject (Using Ember's MutableArray).
And after changing the filter array (filter = filter.filter()) you need to set the new filter variable as the property: App.set('Settings.filter', filter);

Answer 2

The Problem is that I have used .push() to add to App.Settings.filter and .filter() to remove from it. The first approach does not create a new array, the latter does. Thats why removing from that array has worked, but not adding.
I assume that using Ember.ArrayProxy and an observer for .#each would have worked. But thats out of my knowledge. This little problem is solved by just creating a new array though.
filter = App.get('Settings.filter').slice(0);