What *is* the ngModel.$validators pipeline?

Question

While performing some basic research on custom client-side validation in Angular.js, I was reading the ngModel.NgModelController documentation, and found the following cryptic line:

$setValidity(validationErrorKey, isValid); Change the validity state, and notifies the form.

This method can be called within $parsers/$formatters. However, if possible, please use the ngModel.$validators pipeline which is designed to call this method automatically.

A couple of hours and many Google (and StackOverflow!) searches later, I have found nothing about this ngModel.$validators pipeline anywhere. All custom validation examples use the $parsers/$formatters setup as below:

link: function (scope, elem, attr, ctrl) {     // Other necessary logic...      ctrl.$parsers.push(function () {         // Validation logic         ctrl.$setValidity('validation-type', true);     });      ctrl.$formatters.push(function () {         // Validation logic         ctrl.$setValidity('validation-type', true);     }); }, 

Question: The Angular documentation states that the above code is not the best practice, and that this mythical ngModel.$validators pipline is the correct way to go. I have failed to find any information on this better practice. How does one use ngModel.$validators to correctly implement this custom clientside validation?

Answer 1

$validators are new to Angular 1.3. This blog post gives a good explanation on how to use them: http://www.yearofmoo.com/2014/09/taming-forms-in-angularjs-1-3.html#the-validators-pipeline

The basic idea is that you add a function onto ngModel.$validators that returns a boolean specifying whether the model is valid.

Then you can refrence that validator in your HTML the same way you would reference any built in validators. e.g.

<div ng-if="myForm.myField.$error.myValidator">     some error message here </div>