manageAssignmentsCatGrid = function(){
   var colSelect = new Ext.grid.CheckboxSelectionModel();
    var columns = [
        colSelect,
        {header: "Category", id: 'maCatCol',sortable: true, dataIndex: 'category'}
    ];

    manageAssignmentsCatGrid.superclass.constructor.call(this, {
        store: new Ext.data.Store({
            url : 'teacher_tools/gradebook_data.json.php',
            baseParams: {command: 'getCategories'},
            reader: new Ext.data.JsonReader({root: 'getCategories'}, [            
              {name: 'select'},
              {name: 'category'},
              {name: 'drop'},
              {name: 'catid'}
            ]),
              autoLoad : false,
              sortInfo: {
              field: 'category',
              direction: 'ASC'
              }
        }),
        columns: columns,
        ddGroup: 'maDDGroup',
        enableDragDrop: true,
        autoExpandColumn: 'maCatCol',   
        sm:colSelect,
        border: false,
        layout: 'fit',
        autoScroll: true,
        width: 300,  
        id: 'manageAssignmentsCatGrid',
        border: true,
        title: 'Available Categories',
        listeners: {
          rowdblclick : function(grid,index,e){
            grid.ownerCt.chooseRow(grid.store.data.items[index]);
          }                    
        }
    });
}

Ext.extend(manageAssignmentsCatGrid, Ext.grid.GridPanel);