EXT4.0模型定义，和数据加载，以及Grid数据绑定的一个小问题，求帮助

Question

我有如下Ext模型定义Ext.define('UserModel', {
    extend: 'Ext.data.Model',
    idProperty: 'GUID',
    fields: [
        { name: 'GUID', type: 'string' },
        { name: 'NickName', type: 'string' },
        { name: 'Name', type: 'string' },
        { name: 'Cellphone', type: 'string' },
        { name: 'UserName', type: 'string' },
        { name: 'Sex', type: 'string' },
        { name: 'Date', type: 'string' },
        { name: 'IsBaseUser', type: 'boolean' },
        { name: 'IndexUrl', type: 'string' },
        { name: 'AreaName', type: 'string' },
        { name: 'AreaId', type: 'string' },
        { name: 'Birthday', type: 'string' },
    ]
});Ext.define("ComInfoModel", {
    extend: "Ext.data.Model",
    idProperty: 'GUID',
    fields: [
        { name: 'GUID', type: 'string' },
        { name: 'ComName', type: 'string' },
        { name: 'RegName', type: 'string' },
        { name: 'ComLogo', type: 'string' },
        { name: 'ComSite', type: 'string' },
        { name: 'ComUrl', type: 'string' },
        { name: 'ComEmail', type: 'boolean' },
        { name: 'ComPhone', type: 'string' },
        { name: 'BusinessTime', type: 'string' },
        { name: 'BusPath', type: 'string' },
        { name: 'ComLicenseNo', type: 'boolean' },
        { name: 'ComLicensePic', type: 'boolean' },
        { name: 'Legal', type: 'string' },
        { name: 'LegalIdCard', type: 'string' },
        { name: 'LegalPhone', type: 'string' },
        { name: 'AboutCom', type: 'string' },
        { name: 'PersonCount', type: 'string' },
        { name: 'AreaId', type: 'string' },
        { name: 'AreaName', type: 'string' },
        { name: 'ComAdderss', type: 'string' },
        { name: 'IndustryClassId', type: 'string' },
        { name: 'IndustryClassName', type: 'string' },
        { name: 'Products', type: 'string' },
        { name: 'UserAccountId', type: 'string' },
    ]
});
Ext.define("UserAccountModel", {
    extend: "Ext.data.Model",
    idProperty: 'GUID',
    fields: [
        { name: 'GUID', type: 'string' },
        { name: 'Level', type: 'number' },
        { name: 'CertificationLevel', type: 'number' },
        { name: 'OrgType', type: 'number' },
        { name: 'Tags', type: 'string' }
    ],
    hasMany: [
        { name: 'Header', model: 'UserModel' },
        { name: 'MainUser', model: 'UserModel' },
        { name: 'ComInfo', model: 'ComInfoModel' }
    ]
});可以看出：UserAccountModel模型有三个一对一关系，即：Header关联一个UserModel模型，MainUser 关联一个UserModel模型，ComInfo关联一个ComInfoModel模型。
我从服务端直接返回了如下格式的JSON数据(全部数据的一部分)：{
    "DataCount":30,
    "Data":[{
        "GUID":"f8efb990-f215-4da2-aa82-073071209c2a",
        "Level":0,
        "CertificationLevel":0,
        "Header":null,
        "MainUser":{
            "GUID":"edfc6736-17e8-4006-86bb-ceaf3eeeb9f7",
            "NickName":"",
            "Name":null,
            "Cellphone":null,
            "UserName":"",
            "TimeKey":"20110902113051609",
            "Password":"",
            "QuestionOne":null,
            "QuestionTwo":null,
            "QuestionThree":null,
            "AnswerOne":null,
            "AnswerTwo":null,
            "AnswerThree":null,
            "Sex":0,
            "ImAccount":null,
            "ImType":0,
            "UserFace":null,
            "AccountState":0,
            "IsShow":true,
            "Tags":null,
            "Date":"\/Date(1314934251000)\/",
            "IsBaseUser":true,
            "IndexUrl":"dgjiecheng",
            "Info":null,
            "AreaId":"",
            "AreaName":"",
            "AreaDetail":null,
            "RegisteredAreaId":null,
            "RegisteredAreaName":null,
            "Birthday":"\/Date(1314934251000)\/",
            "WorkDate":"\/Date(1314934251000)\/"},
            "OrgType":1,
            "Tags":null
        },
        "ComInfo":{
            "ComName":"",
            "RegName":null,
            "ComLogo":"b7c66e996b1346afb04fe8e6fbefa7a1_20110902.jpg",
            "ComSite":"",
            "ComUrl":"dgjiecheng",
            "ComEmail":null,
            "ComPhone":
            "0769-21395765",
            "BusinessTime":null,
            "BusPath":null,
            "ComLicenseNo":null,
            "ComLicensePic":"e6b89ee74bc8441782dcbc4a06591fb8_20110902.jpg",
            "Legal":"",
            "LegalIdCard":null,
            "LegalPhone":null,
            "AboutCom":"",
            "PersonCount":"50-150人",
            "AreaId":"",
            "AreaName":"",
            "ComAdderss":null,
            "IndustryClassId":"3091676d-bce9-4be0-aba4-430909680ba1",
            "IndustryClassName":"",
            "Products":null,
            "UserAccountId":"f8efb990-f215-4da2-aa82-073071209c2a"
        }
    }
]}
Grid绑定方式如下：var AccountStore = new Ext.data.JsonStore({
    autoDestroy: true,
    storeId: 'AccountStore',
    model: 'UserAccountModel',
    autoLoad: true,
    pageSize: 20,
    proxy: {
        type: 'ajax',
        url: '/Account/GetList',
        actionMethods: "POST",
        reader: {
            type: 'json',
            root: 'Data',
            totalProperty: 'DataCount'
        }
    }
});
    var grid = Ext.create('Ext.grid.Panel', {
        renderTo: Ext.getBody(),
        store: AccountStore,
        selModel: Ext.create('Ext.selection.CheckboxModel'),
        columns: [{
            header: '类型',
            dataIndex: 'OrgType',      
        }, {
            header: '名称',
            dataIndex: 'ComName'//问题在这里(您看到的这种方式无效)，我如何绑定ComInfo中的ComName属性？
        }
    ]