问ng-class的奇怪行为？

EN

  app.filter('groupBy', function () {
        return _.memoize(function (items, field) {
            return _.groupBy(items, field);
        }
        );
    });

$scope.newReg.checkedDomains = [{ "id": "6", "domain": "aaa", "ext": ".net", "status": "true" }, { "id": "7", "domain": "aaa", "ext": ".biz", "status": "false" }, { "id": "15", "domain": "aaa", "ext": ".vn", "status": "false" }];

<div ng-repeat="(key,value) in newReg.checkedDomains | groupBy: 'domain'">   

 <label ng-class="ext.status ? 'check-no' : 'check-yes'" ng-repeat="ext in value">
              <input type="checkbox" ng-click="ext.checked=!ext.checked" value="{{ext.ext}}">
                  {{ext.status}}
     </label>
</div>