ng-options dont select items from resource - angularjs

Question

Iam trying to generate a multiple select-element with ng-options and want to preselect some items. I get the preselected items from a database as an array of objects. That is my HTML markup to build the selectable:
<select ng-model="currentAppointment.services" ng-options="value.id as value.name group by value.group for value in servicegroups"></select>
The currentAppointment.services variable hold the current selected objects. In servicegroups they are all selectable items, which i get from a REST service. The JSON for the servicegroups look like:
[
{
"id": 0,
"name": "Test1"
"price": 20.0
},
{
"id": 1,
"name": "Test2"
}
]
And the currentAppointment JSON:
{
"_id": "1001",
"title" : "test",
"services": [
{
"id": 0,
"name": "Test1"
"price": 20.0
}
]
}
The select-element is created correctly. But the service object with the id 0 is not preselected. I can image that the problem is, that angular compare an normal object against an angularjs Resource-object and so the objects are not equal. Instead the objects should be compared by the id. But how can i achieve that without coding a own directive?

Answer 1

If you want to pre-populate the dropdown list by assigning it with an object, then you need to remove value.id from the comprehension expression.
<select ng-model="currentAppointment.services" ng-options="value.name group by value.group for value in servicegroups"></select>
then do
$scope.currentAppointment.services = $scope.servicegroups[0];
Working Demo