title: require: 'ngModel' in Angular 6/7+
body: <p>I'm working on a simple upper/lower case directive. Since I use ControlValueAccessor I would like to be able to require ngModel directive on a same host element where I apply my appCaseTo directive.</p>
  
  <p>Is there way to do that in Angular? </p>
  
  <p>How to require presence of certain directive from another directive? </p>
  
  <p>Similar to AngularJS with <code>require: 'ngModel'</code> approach.</p>
  
  <pre><code>return {
      require: 'ngModel',
      link: function (scope, element, attrs, modelCtrl) {
  </code></pre>
  
  <p><a href="https://stackblitz.com/edit/angular-upper-lower-case-directive?file=src/app/case-to.directive.ts" rel="nofollow noreferrer">Stackblitz</a> project.</p>