<form ng-controller="SessionController" name="login_form">
  <div class="hide" ng-show='invalid_credentials'>Invalid email/pass</div>
  <input type="submit" value="Login" ng-click='login()'>
</form>

控制器：

utApp.controller('SessionController',($scope,$cookieStore,ClientService) ->
  $scope.login = ->
    ...
    if something
      $scope.invalid_credentials = true
      return

在某些情况下,$scope.invalid_credentials设置为true,但没有显示带错误消息的div.怎么展示它？