title: Ag-Grid and disabling a button
body: <p>I want to disable a button as long as any row is not selected in my ag-grid. When a row is selected I want to activate a button. Here my code:</p>
  
  <p>app.component.html</p>
  
  <pre><code>&lt;button disabled="activeButtons"&gt;Disable me&lt;/button&gt; &lt;!--option 1--&gt;
  &lt;button ng-disabled="activeButtons()"&gt;Disable me&lt;/button&gt; &lt;!--option 2--&gt;
  
  &lt;ag-grid-angular 
       #agGrid
       style="width: 500px; height: 500px;" 
       class="ag-theme-balham"
       [enableSorting]="true"
       [enableFilter]="true"
       [rowData]="rowData | async" 
       [columnDefs]="columnDefs"
       rowSelection="multiple"&gt;
  &lt;/ag-grid-angular&gt;
  </code></pre>
  
  <p>app.component.ts</p>
  
  <pre><code>getSelectedRows() {
    const selectedNodes = this.agGrid.api.getSelectedNodes();
    return selectedNodes == null;
  }
  </code></pre>
  
  <p>How can I notify from the function getSelectedRows to my template button?</p>