n to be associated with a child element
(or &#39;message&#39;) that will show or hide based on the truthiness of that key&#39;s value in the collection. A common use
case for <code>ngMessages</code> is to display error messages for inputs using the <code>$error</code> object exposed by the
<a href="api/ng/directive/ngModel">ngModel</a> directive.</p>
<p>The child elements of the <code>ngMessages</code> directive are matched to the collection keys by a <code>ngMessage</code> or
<code>ngMessageExp</code> dire