$elemM 匹配和更新 [英] $elemMatch and update

问题描述

我想更新使用 $elemMatch 获取的子文档.我在网上找到了一些帖子，但到目前为止我无法让它工作.这就是我所拥有的:

I would like to update a subdocument that was fetched using $elemMatch. I've found some posts online but so far I am not able to get it to work. This is what I have:

架构:

var user = {
  _id: ObjectId
  addresses: [{
    _id: ObjectId
    street: String
  }]
};

代码:

this.findOne({
  'addresses._id': address_id
}, { 'occurrences': { $elemMatch: {
   '_id': address_id
 }}})
  .exec(function(err, doc) {
    if (doc) {
      // Update the sub doc
      doc.addresses[0].street = 'Blah';

      doc.update({ 'addresses': { $elemMatch: { '_id': address_id }}}, { $set: {"addresses.$.street": doc.addresses[0].street }})
        .exec(function(err, count) {
          ...

上述结果导致地址子文档被清除并重新创建一个空白的新文档.如何保存文档/子文档?

The above results in the address sub doc to be wiped out and a blank new one recreated. How can I save the doc/subdoc?

我的目标是能够通过子文档(地址)ID 获取文档(用户)，修改一个匹配的地址然后保存它.

My goal is to be able to fetch a document (user) by subdocument (addresses) ID, modify that one matching address then save it.

推荐答案

您可以通过对模型的单个 update 调用来完成这一切，而不是首先使用 findOne 获取它>:

You can do this all with a single update call on the model instead of fetching it first with findOne:

User.update(
  {'addresses._id': address_id},
  {$set: {'addresses.$.street': 'Blah'}},
  function(err, count) { ... });

这使用位置$$set 中的 > 运算符 只针对查询中匹配的 addresses 元素.

This uses the positional $ operator in the $set to target just the addresses element that was matched in the query.

这篇关于$elemM 匹配和更新的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！