title: Checking for duplicates in while typing in input with ng-model
body: <p>Let's say I have an array like so:</p>
  
  <pre><code>$scope.items = [
      {'name': '1'},
      {'name': '2'},
      {'name': '3'},
  ];
  </code></pre>
  
  <p>Then I have in my template:</p>
  
  <pre><code>&lt;div ng-repeat="x in items"&gt;
      &lt;input ng-model="x.name" /&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Does anyone have any ideas on how I would go about not allowing duplicate names? For example, if someone typed in the <strong>3rd</strong> input box the number <em>1</em>, it wouldn't allow it.</p>