angularjs apply ng-show to a inputs-placehoder-icon

I'd like to change the placeholder-icon of a ionic-input element. Therfore I use a ng-show in two different icons. In the controller I compare two password-fields of equality. If they are equal, a checkmark is shown, if not a decline-icon is shown.

html:

<label class="item item-input">
     <input type="password" name="newPasswordVerify" placeholder="retype new password" ng-model="user.newPasswordVerify"/>
     <i ng-show="passCorrect"  class="icon ion-ios7-close-empty placeholder-icon"></i>
     <i ng-show="!passCorrect"  class="icon ion-ios7-checkmark-empty placeholder-icon" ></i>
</label>

controller:

$scope.$watch('user.newPasswordVerify', function() {

       if($scope.user.newPasswordVerify!=="")
       {
           if($scope.user.newPasswordVerify.equals($scope.user.newPassword))
                   $scope.passCorrect = true;
           else
                   $scope.passCorrect = false;
       }
});

I get a correct console-output, but the dom doesn't apply the changes.

Edit: fiddle

<form name="frm">
  <label class="item item-input">
       <input type="password" name="newPasswordVerify" placeholder="retype new password" ng-model="user.newPasswordVerify"/>
       <i ng-show="passCorrect"  class="icon ion-ios7-close-empty placeholder-icon"></i>
       <i ng-show="!passCorrect"  class="icon ion-ios7-checkmark-empty placeholder-icon" ></i>
  </label>
</form>

When you give a <form> tag a name Angular will assign it a FormController to manage input validation. It's recommended to use that for validation because the life-cycle of model data can varry depending upon how you've setup the form. What's being shown on the page isn't always what is in the model data.

Each ngModel directive will create a ngModelController for that directive that allows you to add $validator rules.

 $scope.frm.newPasswordVerify.$validator.badPassword = function(modelValue,viewValue){
      var value = modelValue || viewValue;
      return $scope.user.newPassword == value;
 };

The above will pass validation (true) if the two passwords match, otherwise it will fail. When it fails the CSS class ng-invalid-bad-password will be assigned to the input. Likewise ng-valid-bad-password when be assigned when true.

The form will have a $error flag set to true for badPassword to match validation.

 <i ng-show="!frm.$error.badPassword"  class="icon ion-ios7-close-empty placeholder-icon"></i>
 <i ng-show="frm.$error.badPassword"  class="icon ion-ios7-checkmark-empty placeholder-icon" ></i>


$scope.user.newPasswordVerify!==""

didn't work. I replaced it with 

$scope.user.newPasswordVerify.charAt(0)

and it works