Knockout checked binding not updating if radio button is deleted - binding

Question

I have a page with a set of radio buttons that is dynamically created by knockout based on the selection of a drop down on the page. This is all working fine but the problem I have is that the "checked" binding on the radio buttons does not seem to be cleared if the radio button is removed due to a change of the drop down. This leaves me with a ViewModel with a value for "checked" when in fact nothing on the view is checked (or at least nothing that can be seen).
What I would expect to happen is that once the radio button is removed the checked binding would go back to being null but I can only assume the binding does not get updated if the radio button is removed from the DOM.
You can see this happening on jsfiddle - basically if you select a radio button and then change the drop down the selected value will still refer to the now removed (and therefore unchecked) radio button.
HTML:
<ul data-bind='foreach: availableChildren'>
<li>
<label>
<input type="radio" name="children" data-bind="checked: $root.selectedChild, value: id" /><span data-bind="text: name"></span>
</label>
</li>
ViewModel:
var ViewModel = function (settings) {
var availableParents = ko.observableArray(settings.parents),
selectedParent = ko.observable(),
availableChildren = ko.computed(function () {
if (!selectedParent()) {
return null;
}
return selectedParent().children;
}),
selectedChild = ko.observable();
return {
availableParents: availableParents,
selectedParent: selectedParent,
availableChildren: availableChildren,
selectedChild: selectedChild,
};
};
Is there anyway to get this to work as I would expect or is this just something that has been missed from Knockout?

Answer 1

I added this snippet to your viewmodel to get the behaviour you wanted:
// create internal computed
ko.computed(function() {
// add dependency to selectedParent
var s = selectedParent();
// reset selectedChild
selectedChild('');
});
Your updated fiddle: http://jsfiddle.net/danne567/avbU7/2/