Question

我正在试图弄清楚如何更新作为帖子一部分的数组中的项目。我确实找到了最接近我正在寻找的东西：MongoDB Update Array element

但我没有特定的帖子排在第一位，就像这个例子似乎表明的那样。但是我需要首先使用_id找到特定的帖子，然后从结果帖子中更新数组中的项目。

我可以使用一个查询执行此操作，还是首先需要找到该项目，然后像其他答案中的示例所示更新它？

在下面的json中我怎么能更新第一篇帖子评论：第一条评论？

编辑：

[{
    "_id": "52c06c86b78a091f26000001",
    "comments": [
        {
            "user_id": "52ad97bab142627664000001 ",
            "username": "phacer",
            "comment": "nice dress!!!",
            "created": 1390668491909,
            "_id": "_SvF-Ag4d6wFf9QR1KdAdFIpcCyI3cqm2F4rl3w7rdk="
        },
        {
            "user_id": "52ad97bab142627664000001 ",
            "username": "phacer",
            "comment": "nice dress!!!",
            "created": 1390668491909,
            "_id": "_SvF-Ag4d6wFf9QR1KdAdFIpcCyI3cqm2F4rl3w7rdk="
        }
    ],
    "desc": "Something somethingson",
    "hate": [],
    "imageurl": "some url",
    "love": [
        {
            "user_id": "52add4f4344e8ca867000001",
            "username": "asd",
            "created": 1390652212592
        }
    ],
    "tags": [
        {
            "y": 29.3,
            "brand": "Zara",
            "type": "Bow Tie",
            "x": 20,
            "color": "Black"
        }
    ],
    "user_id": "52add4f4344e8ca867000001"
},
{
    "_id": "52c06c86b78a091f26000001",
    "comments": [
        {
            "user_id": "52ad97bab142627664000001 ",
            "username": "phacer",
            "comment": "nice dress!!!",
            "created": 1390668491909,
            "_id": "_SvF-Ag4d6wFf9QR1KdAdFIpcCyI3cqm2F4rl3w7rdk="
        }
    ],
    "desc": "Something somethingson",
    "hate": [],
    "imageurl": "some url",
    "love": [
        {
            "user_id": "52add4f4344e8ca867000001",
            "username": "asd",
            "created": 1390652212592
        }
    ],
    "tags": [
        {
            "y": 29.3,
            "brand": "Zara",
            "type": "Bow Tie",
            "x": 20,
            "color": "Black"
        }
    ],
    "user_id": "52add4f4344e8ca867000001"
}]

Answer 1

您应该考虑使用$elemMatch（Documentation），如下所示：

.update({'_id': '52c06c86b78a091f26000001', 'comments' : {$elemMatch: {'_id': '_SvF-Ag4d6wFf9QR1KdAdFIpcCyI3cqm2F4rl3w7rdk='}}}, {$set : {'comments.$.comment': 'Lame dress!'}})

Answer 2

您可以使用Mongo中的位置运算符来访问特定的数组元素，如下所示

db.collection.update( { _id: 52c06c86b78a091f26000001 }, { $set: { "comments.$1.comment" : "dress" } } )

mongodb：更新集合内部帖子内的数组项

2 个答案: