var colModel = new Ext.grid.ColumnModel([
    new Ext.grid.RowNumberer(),//自动行号列模型
    {header: "Name", width: 80, sortable: true},
    {header: "Code", width: 50, sortable: true},
    {header: "Description", width: 200, sortable: true},
    new Ext.grid.RowSelectionModel()//复选框列模型
 ]);