title: orderBy multiple fields in Angular when dropdown is selected
body: <p>How can I use select element to sort an array by mutiple fields? </p>
  
  <pre><code>  &lt;select ng-model="selectedOrder"&gt;
      &lt;option value='id'&gt;id&lt;/option&gt;
      &lt;option value='-id'&gt;-id&lt;/option&gt;
      &lt;option value='country'&gt;country&lt;/option&gt;
      &lt;option value='address'&gt;address&lt;/option&gt;
      &lt;option value='["country","-id"]'&gt;country, -id&lt;/option&gt;
      &lt;option value='["-country","address"]'&gt;-country, address&lt;/option&gt;        
    &lt;/select&gt;
  
  &lt;ul&gt;
    &lt;li ng-repeat="detail in details | filter:{country: countryFilter} | orderBy:selectedOrder"&gt;{{ detail }}&lt;/li&gt;    
  &lt;/ul&gt;
  </code></pre>
  
  <p>If I set order options in a controller everything is fine:<br>
      <code>$scope.selectedOrder = ["country", "-id"];</code></p>
  
  <p>If select option "country, -id" or "-country, address" then sorting not occurs.</p>
  
  <p>Full example here <a href="http://plnkr.co/edit/w968MMN3qT9AB4XXRosV?p=preview" rel="nofollow">http://plnkr.co/edit/w968MMN3qT9AB4XXRosV?p=preview</a></p>