MongoDB (Mongoose) update element in array of array

Question

I'm currently building a REST-Api with node.js express and can't figure out how to update / add elements to the scores Array.

Here is one document from my MongoDB collection (how it should look):

My mongoose model:

const challengesSchema = new mongoose.Schema({
    createdBy:{
        type:String,
        required: true
    },
    mapType:{
        type:String,
        required: true
    },
    time:{
        type:Number,
        required: true
    },
    numberOfMaps:{
        type:String,
        required: true
    },
    maps:{
        type:Array,
        required: true
    },
    pin:{
        type: String,
        required: true
    },
    takenBy:{
        type: Array,
        required: false
    }
})

Basically I receive an id, which I can use to do Challenges.findById({challenge._id}) . I figured out how to add an object to the takenBy Array, like so:

Challenges.findOneAndUpdate(
  { _id: challenge._id },
  {
    $push: {
      takenBy: user
    }
  }
);

How can I add an element (score, like "20") to the scores array in the array 'takenBy' ?

SuleymanSah · Accepted Answer · 2019-12-29 19:57:26Z

3

You can push score and calculate the new TotalScore in one go using filtered positional operator $ like this.

router.put("/challenges/:id/:scoreId", async (req, res) => {
  let score = req.body.score;

  try {
    let result = await Challenges.findByIdAndUpdate(
      req.params.id,
      {
        $push: { "takenBy.$[inner].scores": score },
        $inc: {
          "takenBy.$[inner].TotalScore": score
        }
      },
      {
        arrayFilters: [{ "inner._id": req.params.scoreId }],
        new: true
      }
    );

    if (!result) return res.status(404);

    res.send(result);
  } catch (err) {
    console.log(err);
    res.status(500).send("Something went wrong");
  }
});

Test:

Let's have this existing document:

{
    "_id" : ObjectId("5e08fe4c0bc1b932e8726a0f"),
    "maps" : [ ],
    "takenBy" : [
        {
            "_id" : "id1",
            "TotalScore" : NumberInt(100),
            "scores" : [
                NumberInt(20),
                NumberInt(60),
                NumberInt(20)
            ]
        },
        {
            "_id" : "id2",
            "TotalScore" : NumberInt(30),
            "scores" : [
                NumberInt(10),
                NumberInt(20)
            ]
        }
    ],
    "createdBy" : "5dfe0...",
    "mapType" : "World",
    "time" : NumberInt(2),
    "numberOfMaps" : "2",
    "pin" : "9558",
    "__v" : NumberInt(0)
}

If we want to add a score of 50 to then id1, we send a PUT request (http://..../challenges/5e08fe4c0bc1b932e8726a0f/id1) with this body:

{
    "score": 50
}

The result will be like this:

{
    "_id" : ObjectId("5e08fe4c0bc1b932e8726a0f"),
    "maps" : [ ],
    "takenBy" : [
        {
            "_id" : "id1",
            "TotalScore" : NumberInt(150),
            "scores" : [
                NumberInt(20),
                NumberInt(60),
                NumberInt(20),
                NumberInt(50)
            ]
        },
        {
            "_id" : "id2",
            "TotalScore" : NumberInt(30),
            "scores" : [
                NumberInt(10),
                NumberInt(20)
            ]
        }
    ],
    "createdBy" : "5dfe0...",
    "mapType" : "World",
    "time" : NumberInt(2),
    "numberOfMaps" : "2",
    "pin" : "9558",
    "__v" : NumberInt(0)
}

As you see the score is added to the related item array, and it's TotalScore is also incremented by 50 giving the TotalScore 150

edited Dec 29, 2019 at 19:57

answered Dec 29, 2019 at 19:39

SuleymanSah

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9 Comments

kevinunger Over a year ago

Thanks! Awesome approach! Is there a way I could not just push to the scores array, but can specify the index where to put my new score in that array?

SuleymanSah Over a year ago

@user2557097 yes it seems possible, please have a look at the docs

kevinunger Over a year ago

thanks, it works! Like this:

$push: {              "takenBy.$[inner].scores": {                 $each: [score],                 $position: scorePosition                  },             },

SuleymanSah Over a year ago

@user2557097 great:) You did it by yourself. Please reconsider to accept this answer, this is the way how we update in mongoose.

kevinunger Over a year ago

I accepted your answer. Thanks again! Another problem I can't figure out: The premise of my question was that the takenBy array has objects with ids in it. When the user hasn't submitted a score, it does not add a score. Is there a way to create the object in the taken by array with the corresponding score array and TotalScore in one query? I could find the field and search for the Object with the id, if it exists, execute your query, if not create a new field. Is there a way to do this in one query?

|

Mattia Rasulo · Accepted Answer · 2022-10-10 10:00:08Z

1

You can retrieve the object first:

const updateChallenge = async (req,res) => {
    const challenge = await Challenges.findById(id);
    // Then you make duly changes to it with vanilla js:
    // Find which element in the array takenBy to update 
    // with regular js, methods like filter work or hardcode it

    challenge.takenBy[1].push(newElement);

    await challenge.save();
    // DONE! :)
}

Of course you can use destructuring if you prefer!

edited Oct 10, 2022 at 10:00

answered Dec 29, 2019 at 23:01

Mattia Rasulo

1,54015 silver badges19 bronze badges

Comments

Louys Patrice Bessette · Accepted Answer · 2019-12-29 23:55:58Z

0

...how to update / add elements to the scores Array.

I would first retrieve that array... Push the new value, then update.

Something like:

Challenges.findById(challenge._id,(err, db_result) => {
  if(err){
    console.log(err)              // error management
    //...
  }

  if(db_result){

    // Get the takenBy array
    let takenBy = db_result.takenBy

    // Who are we talking about... You need the second _id for that record
    let who_id = user._id

    let targetIndex = null
    let byWho = takenBy.filter((who, index) => {

      let gotYa = who._id === who_id
      if (gotYa){
        targetIndex = index
      }
      return gotYa  // Boolean used as a return for .filter()
    })

    if(byWho.length>0){
      console.log("Got someone... Index: ", targetIndex)
    }else{
      console.log("No one found?")
      return
    }


    // Push the new value using the index where to update.
    takenBy[targetIndex].scores.push(challenge.score)

    Challenges.updateOne({_id:challenge._id},{
        $set: {
          takenBy: takenBy
        }
      }, (err, data) => {
        console.log(data)
      }
    )

  }
});

edited Dec 29, 2019 at 23:55

answered Dec 29, 2019 at 18:48

Louys Patrice Bessette

34k7 gold badges40 silver badges69 bronze badges

12 Comments

Louys Patrice Bessette Over a year ago

Ho, I missed the fact the score array is in the takenBy array... I will update my answer. But the concept is the same. It's get, push, set. ;)

Louys Patrice Bessette Over a year ago

hahem... Maybe you have to target the right takenBy element... Do you have the second id for it? Hold on a bit more... I'm editing

Louys Patrice Bessette Over a year ago

Try that... ;) We should be close.

kevinunger Over a year ago

It finally works! The problem in the end was that the updateOne function only changes the database document, when it has a callback function, like you did in the first line. I found this link. So everything works now, thanks!

Louys Patrice Bessette Over a year ago

Mind to accept the answer then? I'm happy for you. Enjoy coding!

|

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