datagrid接收json字符串中的内嵌对象

columns:[[
				      	{field:'ck',checkbox:true},  
				      	{field:'userId',title:'用户ID',align:'center',width:80,editor:'text',
					      	formatter:function(val,rec)
					      	{
					      	return val = rec.id.userId;
					      	}
				      	}, 
				      	{field:'id.sxh',title:'顺序号',align:'center',width:50,editor:'text'},
				      	{field:'yhzdymc.zdyflno',title:'自定义分类顺序',width:100,align:'center',editor:'text'},
				      	{field:'zylx',title:'资源类型',width:80,align:'center',editor:'text'},
				      	{field:'zybh',title:'资源编号',width:60,align:'center',editor:'text'},
				      	{field:'sskcmc',title:'所属课程名称',width:80,align:'center',editor:'text'},
				      	{field:'zyms',title:'资源描述',width:386,align:'center',editor:'text'} 
				      	]],

　　接收到的json串为：

[JSON]{"page":1,"rows":[{"id":{"sxh":14,"userId":"admin"},"sskcmc":null,"userinfo":{"roles":{"miaoshu":"admin","roleid":106,"rolename":"1"},"safeAnswer":null,"safeQuestion":null,"type":null,"typeId":null,"userId":"admin","userPw":"123"},"yhzdymc":{"userinfo":{"roles":{"miaoshu":"admin","roleid":106,"rolename":"1"},"safeAnswer":null,"safeQuestion":null,"type":null,"typeId":null,"userId":"admin","userPw":"123"},"zdyflmc":null,"zdyflno":3,"zysl":null},"zybh":null,"zylx":null,"zyms":null}],"rows_s":10,"total":1}

　　我在field：'userId'字段中想取得userId的值就可以加入formatter参数：

formatter:function(val,rec)
					      	{
					      	return val = rec.id.userId;
					      	}