title: AngularJS - how to change the value of ngModel in custom directive?
body: <p>Lets take a look to my directive:</p>
  
  <pre><code>angular.module('main').directive('datepicker', [
  function() {
      return {
          require: '?ngModel',
          link: function(scope, element, attributes, ngModel) {
              ngModel.$modelValue = 'abc'; // this does not work
              // how do I change the value of the model?
  </code></pre>
  
  <p>So, how do I change the value of the ng-model?</p>