Extjs 4 如何列舉表單欄位,並一口氣把所有有問題欄位告知user

        var me = this;
        if (!this.getForm().isValid()) {
            //findout invalid fields
            var fields = me.getForm().getFields();
            var errorField = '';
            for (var i = 0; i < fields.getCount() ; i++) {
                var field = fields.getAt(i);
                if (!field.isValid()) {
                    if (errorField.length > 0) errorField += "<br>";
                    errorField += field.getFieldLabel();
                }
            }
            Ext.Msg.alert('Validate failed in field(s):<br>'+errorField);
            return;
        }