如何从外部函数更新对象？

Question

在这个猫鼬功能上苦苦挣扎。我正在尝试在另一个嵌入对象中添加一个嵌入对象，但它将新的出价对象添加到错误的位置 - 我为迭代器创建的新列表变量。 我的 for 循环试图找到要更新的确切列表，所以我认为分配它们的操作会弄乱它们。例如，如果列表是 users[2].listings[10].bids ，我如何获取该对象以便更新它？

 function create(req, res) {
   db.Listing.findById(req.params.listingId, function(err, foundListing) {
    // console.log(foundListing._id );
    if (err) {
      console.log('Error', err);
    }
     // res.json(foundListing);
     // get array of all users
    db.User.find({}, function(err, users) {
      // for loop iterates through all users' listings
      for (let i = 0; i < users.length; i++) {
        let listings = users[i].listings
        // for loop iterates through all listings ids
        for (let j = 0; j < listings.length; j++) {
          // finds match
          // comparing _id with _id returning false. Not sure why, will return later
          if (listings[j].topic === foundListing.topic && listings[j].created === foundListing.created) {
            console.log("Found match: " + foundListing.topic);
            // get current user id to add to bid object
            db.User.findById(req.user, function(err, user) {
              if (err) {
                console.log(err);
              }
              var newBid = new db.Bid(req.body); // add data validation later
              newBid.uid = user._id
              // pushes new bid object into embedded listing
              listings[j].bids.push(newBid);
              listings[j].save(function(err, savedBid) {
               console.log('newBid created: ', newBid);
               console.log(listings[j]);
               res.json(newBid);
              });
            });
          }
        }
      }
    })
    if (err) {
      console.log(err);
    }
  });
};

编辑 - 到目前为止，但现在我的数组似乎没有保存。

function create(req, res) {
  db.Listing.findById(req.params.listingId, function(err, foundListing) {
    if (err) {
      console.log('Error:', err);
    }
    db.User.findOne({ 'listings._id': req.params.listingId }, function(err, foundUser) {
      // console.log(foundUser.listings);
      if (err) {
        console.log('Error: ', err);
      }
      for (let i = 0; i < foundUser.listings.length; i++) {
        // console.log(foundUser.listings[i]._id);
        if (foundUser.listings[i]._id == req.params.listingId) {
          console.log( 'found it! - ' + foundUser.listings[i].topic);
          var newBid = new db.Bid(req.body);
          // console.log(newBid)
          foundUser.listings[i].bids.push(newBid);
          console.log(foundUser.listings[i].bids)
          foundUser.listings[i].save(function(err, savedListing) {
            // console.log(foundUser.listings[i])
            if (err) {
              console.log('Error: ', err);
              return;
            }
              console.log('newBid created: ', newBid);
              console.log('savedListing', savedListing);
              res.json(newBid);
          })
        }
      }
    })
  });
};

Answer 1

您拥有的代码很难掌握。我认为您可能使用了错误的工具来解决问题。 MongoDb 和 Mongoose 似乎具有相当高级的查询功能，因此您可以指定您感兴趣的确切用户、列表等。

我认为值得您花时间查看Mongoose queries 和MongoDb queries 的文档。在db.User.findOne({ 'listings.id': req.params.listingId } 中用于listings.id 的. 是described here。

我无法真正测试此代码是否可以编译或是否可以工作，因为我对您的数据库模型等了解不够，但是应该可以进行以下操作：

 function create(req, res) {
   db.Listing.findById(req.params.listingId, function(err, foundListing) {
    // use the power of mongo db and mongoose.
    // you can specify more exactly what you're looking for
    // in this case we're interested in ONE user that
    // has a listing with a specific id  
    // (if you still problems with comparing identical IDs, then that's a serious issue..
    //  maybe try logging req.params.listingId and check if it really exists
    // in your database.)
    db.User.findOne({ 'listings.id': req.params.listingId }, function(err, foundUser) {
      var newBid = new db.Bid(req.body); // add data validation later
      newBid.uid = foundUser._id

      // Old code: foundListing.bids.push(newBid) 

      // Change according to first question/answer at  http://mongoosejs.com/docs/faq.html
      // which was linked in the thread you linked to in comment.
      // The essence is that Mongoose doesn't get
      // notified about changes to arrays by default
      // To get around this you can update using "set"
      // but then you need both a value and an index:
      var oldBidsLength = foundListing.bids.length;
      foundListing.bids.set(oldBidsLength, newBid);     

      foundListing.save(function(err, savedBid) {
        // savedBid  =  saved LISTING? 
        console.log('newBid created: ', newBid);
        console.log('savedBid', savedBid);
        res.json(savedBid);
        }
      }
    })
  });
};

此代码示例可能会出现问题，例如 db.User.findOne({ 'listings.id': req.params.listingId } 是否应该与 listings._id 一起使用。我对你的模型了解不够。