title: AngularJS ng-class not applying bootstrap error classes
body: <p>I'm building a multi-step AngularJS form that adds bootstrap error classes on ng-class. I'm using this tutorial as my base for building the form <a href="http://scotch.io/tutorials/javascript/angularjs-multi-step-form-using-ui-router#building-our-angular-app-app.js" rel="nofollow">http://scotch.io/tutorials/javascript/angularjs-multi-step-form-using-ui-router#building-our-angular-app-app.js</a>.</p>
  
  <p><strong>Question:</strong> Why are my ng-class css classes not being applied to my form-group wrapper when child fields are invalid? My submit button stays disabled until form fields are correct, but error classes and styling never gets applied.</p>
  
  <p><strong>HTML</strong></p>
  
  <pre><code>&lt;div class="form-group" ng-class="{'has-error has-feedback' : longForm.fullName.$invalid &amp;&amp; !longForm.fullName.$pristine}"&gt;
    &lt;label class="hidden-xs" for="FullName"&gt;Full Name&lt;/label&gt;
    &lt;input class="form-control input-lg" type="text" name="FullName" placeholder="Your Full Name" ng-model="longFormData.fullName" required /&gt;
  &lt;/div&gt;
  &lt;div class="form-group"&gt;
    &lt;button class="btn btn-cta btn-lg btn-block" type="submit" ng-disabled="longForm.$invalid"&gt;Next&lt;/button&gt;
  &lt;/div&gt;
  </code></pre>