app.directive('dropdown', function ($timeout) {
    return {
        restrict: 'E',
        template: '<div class="btn-group" dropdown>' +
             '<button id="dropdownDirective" class="btn dropdown-toggle" dropdown-toggle>' +
                '{{ items[ngModel].name }}' +
                '<span class="caret"></span>' +
            '</button>' +
            '<ul class="dropdown-menu" role ="menu" aria-label="dLabel">' +
                '<li ng-repeat="item in items">'+
                    '<a href="#" ng-bind="item.name" ng-click = "select(item)" >< / a >' +
                '</li>'+
            '</ul>'+
            '</div>',
        scope: {
            ngModel: '=', // selected option
            items: '=',   // options
        },
        link: function (scope, element, attrs) {
            scope.select = function (item) {
                scope.ngModel = item.id;
            };
        }
    };
});

<dropdown id="modalSelect"
    ng-model="ahs.modal.modalId"
    items="es.modal.data">
    </dropdown>

app.directive('dropdown', function ($timeout) {
      return {
          require: "ngModel",
          restrict: 'E',
          template: [...]
          scope: {
              items: '=',   // options
          },
          link: function (scope, element, attrs, ngModelController) {
              ngModelController.$setViewValue(...);
              ngModelController.$setPristine(...);
              etc.
          }
      };
  });