title: Binding an Angular Directive property to a parent Controller
body: <p>In the ma-resource-text-watch Directive I make an api call to get a list of resource texts.
  I want to be able to hide the alert-component if the api doesn't return any resource texts.
  Does anyone know how I might be able to do this?</p>
  
  <pre><code>&lt;div ng-controller="IntroductionCntrl" class="hidden-print"&gt;
      &lt;div class="container-fluid" ng-if="introductionResourceKey"&gt;
          &lt;alert-component type="guidance"&gt;
              &lt;span ma-resource-text-watch="{{introductionResourceKey}}"&gt;&lt;/span&gt;
          &lt;/alert-component&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>