item selected and selectable in ui-select2 - angularjs

Question

Usually, an item is removed from the list of selectable items, after being selected.
But, when I refresh the underlying list of items, the (already) selected items, are selectable too!
How can i avoid this?
My view looks like this:
<div ng-controller="MyCtrl" ng-init=buildList()>
<button ng-click="buildList()">Refresh list</button>
<select multiple ui-select2 data-ng-model="selectedDaltons">
<option data-ng-repeat="dalton in daltons" value="{{dalton.id}}">
{{dalton.name}}
</option>
</select>
</div>
My controller:
function MyCtrl($scope) {
// Averell is preselected (id:4)
$scope.selectedDaltons = [4];
// $scope.daltons is iterated in ng-repeat
// its initially called in ng-init
$scope.buildList = function() {
$scope.daltons = [
{ id: 1, name: 'Joe' },
{ id: 2, name: 'William' },
{ id: 3, name: 'Jack' },
{ id: 4, name: 'Averell' },
{ id: 5, name: 'Ma' }
];
};
};
Here it is as a jsfiddle.

Answer 1

Actually I think I found an solution (to my own question):
Based on the controller of the original question, change the array, before replacing it:
function MyCtrl($scope) {
// Averell is preselected (id:4)
$scope.selectedDaltons = [4];
// $scope.daltons is iterated in ng-repeat
// its initially called in ng-init
$scope.buildList = function() {
// touch array before renewal!!
if (angular.isArray($scope.daltons)) {
$scope.daltons.pop();
}
$scope.daltons = [
{ id: 1, name: 'Joe' },
{ id: 2, name: 'William' },
{ id: 3, name: 'Jack' },
{ id: 4, name: 'Averell' },
{ id: 5, name: 'Ma' }
];
};
};
Here the updated jsfiddle.