title: Angular - Multiple fields in ng-messages
body: <p>I'm using <code>ng-messages</code> and want to know if its possible to check across multiple fields in one block of code rather than having to repeat:</p>
  
  <p>So I have:
  (note <code>checkCustom</code> is a custom directive I have wrote)</p>
  
  <pre><code>&lt;div ng-messages="registrationForm.field1.$error" ng-if="registrationFormValid"&gt;
      &lt;span ng-message="required"&gt;please enter field 1&lt;/span&gt;
      &lt;span ng-message="checkCustom"&gt;please check custom value&lt;/span&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>and</p>
  
  <pre><code>&lt;div ng-messages="registrationForm.field2.$error" ng-if="registrationFormValid"&gt;
      &lt;span ng-message="required"&gt;please enter field 1&lt;/span&gt;
      &lt;span ng-message="checkCustom"&gt;please check custom value&lt;/span&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>However I'd much rather something like:</p>
  
  <pre><code>&lt;div ng-messages="registrationForm.field1.$error || registrationForm.field2.$error" ng-if="registrationFormValid"&gt;
      &lt;span ng-message="required"&gt;please enter field 1&lt;/span&gt;
      &lt;span ng-message="checkCustom"&gt;please check custom value&lt;/span&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Is something like this possible?</p>
  
  <p>Thanks</p>