Ext.ux.grid.GridSummary() is not a constructor

I found several examples how to use Ext.ux.grid.GridSummary() in GridPanel, main problem here is if I try to summary plugin on this way:

plugins: new Ext.ux.grid.GridSummary(),

I get JS error that 开发者_运维百科Ext.ux.grid.GridSummary() is not a constructor?!

Any idea about this or hint?

Did you include the correct JavaScript file? The ux-namespace is not part of the standard ExtJS distribution and must be included manually. You must include

<!-- base library --> 
<link rel="stylesheet" type="text/css" href="/path/to/resources/css/ext-all.css" />
<!-- extensions --> 
<link rel="stylesheet" type="text/css" href="/path/to/GroupSummary.css" />
...
<!-- ExtJS library: base/adapter --> 
<script type="text/javascript" src="/path/to/adapter/ext/ext-base.js"></script> 
<!-- ExtJS library: all widgets --> 
<script type="text/javascript" src="/path/to/ext-all.js"></script> 
<!-- extensions --> 
<script type="text/javascript" src="/path/to/GroupSummary.js"></script> 

EDIT:

Just noticed: shouldn't it be Ext.ux.grid.GroupSummary?