title: Angular - Smart-table - OR in filter
body: <p>I'm using the very good <a href="https://github.com/lorenzofox3/Smart-Table" rel="nofollow">Smart-table</a> library to display my data. I have made a custom filter directive to allow me to assign filters to buttons, so that users can easily filter by row state (i.e. 'New', 'Done', 'Failed' etc). This works fine, but I'd like to be able to compound filters so that I could filter by rows containing one of two values in the state column (for instance 'New' and 'Failed').</p>
  
  <p>My custom filter looks like....</p>
  
  <pre><code>app.directive('stCustomFilter', function() {
      return {
          restrict: 'A',
          require: '^stTable',
          scope: true,
          link: function(scope, element, attr, ctrl) {
              var tableState = ctrl.tableState();
              var searchText = attr.stCustomFilter;
              var searchColumn = attr.stCustomFilterColumn;
  
              element.on('click', function(data) {
                  tableState.search.predicateObject = {};
                  ctrl.search(searchText, searchColumn);
                  //console.log(tableState);
                  scope.$apply();
              })
          }
      };
  });
  </code></pre>
  
  <p>and is used as follows inside the st-table's thead.....</p>
  
  <pre><code>&lt;div class="btn-group  btn-group-sm"&gt;
      &lt;button st-custom-filter="" st-custom-filter-column="status"&gt;All&lt;/button&gt;
      &lt;button st-custom-filter="New" st-custom-filter-column="status"&gt;New&lt;/button&gt;
      &lt;button st-custom-filter="Done" st-custom-filter-column="status"&gt;Done&lt;/button&gt;
      &lt;button st-custom-filter="Failed" st-custom-filter-column="status"&gt;Failed&lt;/button&gt;
  &lt;/div&gt; 
  </code></pre>
  
  <p>So ideally, I'd like to be able to use something like "New||Failed" inside the st-custom-filter by altering the directive slightly, but I have a feeling that the answer may lie in writing something more complex involving the st-pipe method.</p>
  
  <p>Can anyone offer a suggestion or two? Many thanks.</p>