mongodb 更新数组出现can't append to array using string field name

数据库内容大概如下：

{
_id:,
"hero_list" : {
             "" : {
                        "stars" : ,
                        "_id" : ,
                        "equip" : [
                                [ ],
                                [ ],
                                [ ],
                                {
                                        "item_id" : ,
                                        "lv" : ,
                                        "uuid" : "4a727ee1-e7b0-4265-b004-e2b75890378a",
                                        "amount" :
                                },
                                [ ],
                                [ ]
                        ],
                        "lv" : ,
                        "exp" : ,
                        "quality" :
                }
            }
}

> db.hero.update({_id:1},{$set:{"hero_list.15521.equip.4.lv":1}})
can't append to array using string field name [lv]

看了半天，原来是自己眼花，数组下标数错了

db.hero.update({_id:1},{$set:{"hero_list.15521.equip.3.lv":1}})

OK