修改ExtJs store默认的排序行为

ExtJs2.0的时候，普通的Ext.data.SimpleStore的对数据的排序行为是区分大小写的。 比如有如下几个name,

[list]
1,Ashely,
2,amonda
3,Cary
[/list]

经过ExtJs SimpleStore排序后，出现的顺序如下：

[list]
1,Ashely,
2,Cary
3,amonda
[/list]

因为ExtJs内部是按照ASCII排序的，而在ASCII中，大写字母总在小写字母之前。

需要修改行为，使得排序不分区大小写。下面是我的实现，不通用，但是在这个例子是跑的通。

例子是ExtJs官方的的array_grid的例子,[url]http://www.extjs.com/deploy/dev/examples/grid/array-grid.html[/url]

下面是我修改过的代码，array-grid.js

/*
 * Ext JS Library 2.2.1
 * Copyright(c) 2006-2009, Ext JS, LLC.
 * [email protected]
 * 
 * http://extjs.com/license
 */

Ext.onReady(function(){

    // NOTE: This is an example showing simple state management. During development,
    // it is generally best to disable state management as dynamically-generated ids
    // can change across page loads, leading to unpredictable results.  The developer
    // should ensure that stable state ids are set for stateful components in real apps.
    Ext.state.Manager.setProvider(new Ext.state.CookieProvider());

        //覆盖的排序在这里起作用。
	Ext.data.CustomSortStore = Ext.extend(Ext.data.SimpleStore,{
		sortData : function(f, direction){
			direction = direction || 'ASC';
			var st = this.fields.get(f).sortType;
			var fn = function(r1, r2 , store){
				var v1 = st(r1.data[f]), v2 = st(r2.data[f]);
				if(typeof(v1) == 'string' && typeof(v2) == 'string'){                              
                                        //去掉大小写限制
					var al = v1.toLowerCase(), bl= v2.toLowerCase();
					return al > bl ? 1 : (al < bl ? -1 : 0);
				}else{
					return v1 > v2 ? 1 : (v1 < v2 ? -1 : 0);
				}
			};

			this.data.sort(direction, fn);
			if(this.snapshot && this.snapshot != this.data){
				this.snapshot.sort(direction, fn);
			}
		}
	});

    var myData = [
        ['3m Co',71.72,0.02,0.03,'9/1 12:00am'],
		['citigroup, Inc.',49.37,0.02,0.04,'9/1 12:00am'],
        ['Altria Group Inc',83.81,0.28,0.34,'9/1 12:00am'],
        ['American Express Company',52.55,0.01,0.02,'9/1 12:00am'],
        ['American International Group, Inc.',64.13,0.31,0.49,'9/1 12:00am'],
        ['AT&T Inc.',31.61,-0.48,-1.54,'9/1 12:00am'],
        ['Boeing Co.',75.43,0.53,0.71,'9/1 12:00am'],
        ['Caterpillar Inc.',67.27,0.92,1.39,'9/1 12:00am'],
        ['E.I. du Pont de Nemours and Company',40.48,0.51,1.28,'9/1 12:00am'],
		['alcoa Inc',29.01,0.42,1.47,'9/1 12:00am'],
        ['Exxon Mobil Corp',68.1,-0.43,-0.64,'9/1 12:00am'],
        ['General Electric Company',34.14,-0.08,-0.23,'9/1 12:00am'],
        ['General Motors Corporation',30.27,1.09,3.74,'9/1 12:00am'],
        ['Hewlett-Packard Co.',36.53,-0.03,-0.08,'9/1 12:00am'],
        ['Honeywell Intl Inc',38.77,0.05,0.13,'9/1 12:00am'],
        ['Intel Corporation',19.88,0.31,1.58,'9/1 12:00am'],
        ['International Business Machines',81.41,0.44,0.54,'9/1 12:00am'],
        ['Johnson & Johnson',64.72,0.06,0.09,'9/1 12:00am'],
        ['JP Morgan & Chase & Co',45.73,0.07,0.15,'9/1 12:00am'],
        ['mcDonald\'s Corporation',36.76,0.86,2.40,'9/1 12:00am'],
        ['Merck & Co., Inc.',40.96,0.41,1.01,'9/1 12:00am'],
        ['Microsoft Corporation',25.84,0.14,0.54,'9/1 12:00am'],
        ['Pfizer Inc',27.96,0.4,1.45,'9/1 12:00am'],
        ['The Coca-Cola Company',45.07,0.26,0.58,'9/1 12:00am'],
        ['The Home Depot, Inc.',34.64,0.35,1.02,'9/1 12:00am'],
        ['The Procter & Gamble Company',61.91,0.01,0.02,'9/1 12:00am'],
        ['United Technologies Corporation',63.26,0.55,0.88,'9/1 12:00am'],
        ['Verizon Communications',35.57,0.39,1.11,'9/1 12:00am'],
        ['Wal-Mart Stores, Inc.',45.45,0.73,1.63,'9/1 12:00am']
    ];

    // example of custom renderer function
    function change(val){
        if(val > 0){
            return '' + val + '';
        }else if(val < 0){
            return '' + val + '';
        }
        return val;
    }

    // example of custom renderer function
    function pctChange(val){
        if(val > 0){
            return '' + val + '%';
        }else if(val < 0){
            return '' + val + '%';
        }
        return val;
    }

    // create the data store
    // 这里使用我们自定义的Store
    var store = new Ext.data.CustomSortStore({
        fields: [
           {name: 'company'},
           {name: 'price', type: 'float'},
           {name: 'change', type: 'float'},
           {name: 'pctChange', type: 'float'},
           {name: 'lastChange', type: 'date', dateFormat: 'n/j h:ia'}
        ]
    });

    store.loadData(myData);

    // create the Grid
    var grid = new Ext.grid.GridPanel({
        store: store,
        columns: [
            {id:'company',header: "Company", width: 160, sortable: true, dataIndex: 'company'},
            {header: "Price", width: 75, sortable: true, renderer: 'usMoney', dataIndex: 'price'},
            {header: "Change", width: 75, sortable: true, renderer: change, dataIndex: 'change'},
            {header: "% Change", width: 75, sortable: true, renderer: pctChange, dataIndex: 'pctChange'},
            {header: "Last Updated", width: 85, sortable: true, renderer: Ext.util.Format.dateRenderer('m/d/Y'), dataIndex: 'lastChange'}
        ],
        stripeRows: true,
        autoExpandColumn: 'company',
        height:350,
        width:600,
        title:'Array Grid'
    });

    grid.render('grid-example');
});

排序结果：
[img]http://dl.iteye.com/upload/attachment/182030/5b0bd629-4c50-36c3-9cb7-bf41e05cabe4.jpg[/img]
----------------
这里的办法可以实现修改排序行为,但是却不通用。我想要的是一种可以覆盖Ext.data.Store的行为的方式，可以方便在new instance的时候注入sort function.我有试着这样去写：

//省略其他
	Ext.apply(Ext.data.Store,{
		sortFn : undefined,
		sortData : function(f, direction){
			direction = direction || 'ASC';
			var st = this.fields.get(f).sortType;
			var fn = function(r1, r2 , store){
				var v1 = st(r1.data[f]), v2 = st(r2.data[f]);
				if(this.sortFn && typeof(this.sortFn) == 'function'){
					return this.sortFn(v1,v2);
				}else{
					return v1 > v2 ? 1 : (v1 < v2 ? -1 : 0);
				}
			};

			this.data.sort(direction, fn);
			if(this.snapshot && this.snapshot != this.data){
				this.snapshot.sort(direction, fn);
			}
		}
	});

	// 省略其他
       // 构造store的时候传入排序函数：
    var store = new Ext.data.CustomSortStore({
        fields: [
           {name: 'company'},
           {name: 'price', type: 'float'},
           {name: 'change', type: 'float'},
           {name: 'pctChange', type: 'float'},
           {name: 'lastChange', type: 'date', dateFormat: 'n/j h:ia'}
        ],
		sortFn : function(v1,v2){
			if(typeof(v1) == 'string' && typeof(v2) == 'string'){
				var v1l = v1.toLowerCase(),v2l = v2.toLowerCase();
				return return v1l > v2l ? 1 : (v1l < v2l ? -1 : 0);
			}else{
				return v1 > v2 ? 1 : (v1 < v2 ? -1 : 0);
			}
		}
    });

但是这样做不起任何作用，实际排序的时候走的还是Ext.data.Store的默认的sortData方法，并不能覆盖。

我想问问，怎么样才能实现我想的那种效果？