AngularJS在自定义指令中包含ui-select

this.adminv2.directive('eventSelect',function() {
    return {
      restrict: 'E',replace: true,scope: {
        ngModel: '=',placeholder: '='
      },controller: function($scope,$http) {
        return $scope.refreshEvents = function(searchTerm) {
          return $http.get('/events/autocomplete',{
            params: {
              term: searchTerm
            }
          }).then(function(response) {
            return $scope.events = response.data;
          });
        };
      },template: "<div>{{ngModel}}n  <ui-select ng-model="ngModel"n             theme="bootstrap"n             ng-disabled="disabled"n             reset-search-input="false">n    <ui-select-match placeholder="Enter an event">{{$select.selected.name}}</ui-select-match>n    <ui-select-choices repeat="event in events track by $index"n             refresh="refreshEvents($select.search)"n             refresh-delay="0">n      <span ng-bind-html="event.name | highlight: $select.search"></span>n      <i class="icon-uniF111 fg type-{{raceType}} pull-right" ng-repeat='raceType in event.racetypes'></i>n      <br>n      {{event.dates}} <i class='pull-right'>{{event.location}}</i>n    </ui-select-choices>n  </ui-select>n</div>"
    };
  });

选择正常,但与ng模型的绑定不起作用.我无法设置模型或阅读它.
我没有得到它,因为它使用一个简单的模板,如

<div><input ng-model="ngModel"></div>

有什么特别的事要做,因为我在指令中包装了一个指令吗？