How to define object in array in Mongoose schema correctly with 2d geo index

I'm currently having problems in creating a schema for the document below. The response from the server always returns the "trk" field values as [Object]. Somehow I have no idea how this should work, as I tried at least all approaches which made sense to me ;-)

If this helps, my Mongoose version is 3.6.20 and MongoDB 2.4.7 And before I forget, it would be nice to also set it as Index (2d)

Original data:

{
    "_id": ObjectId("51ec4ac3eb7f7c701b000000"),
    "gpx": {
        "metadata": {
            "desc": "Nürburgring VLN-Variante",
            "country": "de",
            "isActive": true
        },
    "trk": [
    {
        "lat": 50.3299594,
        "lng": 6.9393006
    },
    {
        "lat": 50.3295046,
        "lng": 6.9390688
    },
    {
        "lat": 50.3293714,
        "lng": 6.9389939
    },
    {
        "lat": 50.3293284,
        "lng": 6.9389634
    }]
    }
}

Mongoose Schema:

var TrackSchema = Schema({
            _id: Schema.ObjectId,
            gpx: {
                metadata: {
                    desc: String,
                    country: String,
                    isActive: Boolean
                },
                trk: [{lat:Number, lng:Number}]
            }
        }, { collection: "tracks" });

The response from the Network tab in Chrome always looks like this (that's only the trk-part which is wrong) :

{ trk: 
      [ [Object],
        [Object],
        [Object],
        [Object],
        [Object],
        [Object],

I already tried different Schema definitions for "trk":

1. trk: Schema.Types.Mixed
2. trk: [Schema.Types.Mixed]
3. trk:[ { type:[Number], index: "2d" }]

Hope you can help me ;-)

You can declare trk by the following ways : - either

trk : [{
    lat : String,
    lng : String
     }]

or

trk : { type : Array , "default" : [] }

In the second case during insertion make the object and push it into the array like

db.update({'Searching criteria goes here'},
{
 $push : {
    trk :  {
             "lat": 50.3293714,
             "lng": 6.9389939
           } //inserted data is the object to be inserted 
  }
});

or you can set the Array of object by

db.update ({'seraching criteria goes here ' },
{
 $set : {
          trk : [ {
                     "lat": 50.3293714,
                     "lng": 6.9389939
                  },
                  {
                     "lat": 50.3293284,
                     "lng": 6.9389634
                  }
               ]//'inserted Array containing the list of object'
      }
});

I had a similar issue with mongoose :

fields: 
    [ '[object Object]',
     '[object Object]',
     '[object Object]',
     '[object Object]' ] }

In fact, I was using "type" as a property name in my schema :

fields: [
    {
      name: String,
      type: {
        type: String
      },
      registrationEnabled: Boolean,
      checkinEnabled: Boolean
    }
  ]

To avoid that behavior, you have to change the parameter to :

fields: [
    {
      name: String,
      type: {
        type: { type: String }
      },
      registrationEnabled: Boolean,
      checkinEnabled: Boolean
    }
  ]

For making an array in schema we have to make one more schema as monetizationSchema which is used to store one data at a time and another as blogSchema we have monetization field containing monetizationSchema in square brackets as an array.

Schema for storing one data at a time.

const monetizationSchema = new Schema({
      amazonUrl: {
        type: String,
        required: true,
      } 
    });

Schema with monetization as an array.

const blogSchema = {
  monetization: [
   monetizationSchema
  ],
  image: {
   type: String,
   required: true
  },
  // ... etc
});

The problem I need to solve is to store contracts containing a few fields (address, book, num_of_days, borrower_addr, blk_data), blk_data is a transaction list (block number and transaction address). This question and answer helped me. I would like to share my code as below. Hope this helps.

> 1. Schema definition. See blk_data.

var ContractSchema = new Schema(
    {
        address: {type: String, required: true, max: 100},  //contract address
        // book_id: {type: String, required: true, max: 100},  //book id in the book collection
        book: { type: Schema.ObjectId, ref: 'clc_books', required: true }, // Reference to the associated book.
        num_of_days: {type: Number, required: true, min: 1},
        borrower_addr: {type: String, required: true, max: 100},
        // status: {type: String, enum: ['available', 'Created', 'Locked', 'Inactive'], default:'Created'},

        blk_data: [{
            tx_addr: {type: String, max: 100}, // to do: change to a list
            block_number: {type: String, max: 100}, // to do: change to a list
        }]
    }
);

> 2. Create a record for the collection in the MongoDB. See blk_data.

// Post submit a smart contract proposal to borrowing a specific book.
exports.ctr_contract_propose_post = [

    // Validate fields
    body('book_id', 'book_id must not be empty.').isLength({ min: 1 }).trim(),
    body('req_addr', 'req_addr must not be empty.').isLength({ min: 1 }).trim(),
    body('new_contract_addr', 'contract_addr must not be empty.').isLength({ min: 1 }).trim(),
    body('tx_addr', 'tx_addr must not be empty.').isLength({ min: 1 }).trim(),
    body('block_number', 'block_number must not be empty.').isLength({ min: 1 }).trim(),
    body('num_of_days', 'num_of_days must not be empty.').isLength({ min: 1 }).trim(),

    // Sanitize fields.
    sanitizeBody('*').escape(),
    // Process request after validation and sanitization.
    (req, res, next) => {

        // Extract the validation errors from a request.
        const errors = validationResult(req);
        if (!errors.isEmpty()) {
            // There are errors. Render form again with sanitized values/error messages.
            res.status(400).send({ errors: errors.array() });
            return;
        }

        // Create a Book object with escaped/trimmed data and old id.
        var book_fields =
            {
                _id: req.body.book_id, // This is required, or a new ID will be assigned!
                cur_contract: req.body.new_contract_addr,
                status: 'await_approval'
            };

        async.parallel({
            //call the function get book model
            books: function(callback) {
                Book.findByIdAndUpdate(req.body.book_id, book_fields, {}).exec(callback);
            },
        }, function(error, results) {
            if (error) {
                res.status(400).send({ errors: errors.array() });
                return;
            }

            if (results.books.isNew) {
                // res.render('pg_error', {
                //     title: 'Proposing a smart contract to borrow the book',
                //     c: errors.array()
                // });
                res.status(400).send({ errors: errors.array() });
                return;
            }

            var contract = new Contract(
                {
                    address: req.body.new_contract_addr,
                    book: req.body.book_id,
                    num_of_days: req.body.num_of_days,
                    borrower_addr: req.body.req_addr

                });

            var blk_data = {
                    tx_addr: req.body.tx_addr,
                    block_number: req.body.block_number
                };
            contract.blk_data.push(blk_data);

            // Data from form is valid. Save book.
            contract.save(function (err) {
                if (err) { return next(err); }
                // Successful - redirect to new book record.
                resObj = {
                    "res": contract.url
                };
                res.status(200).send(JSON.stringify(resObj));
                // res.redirect();
            });

        });

    },
];

> 3. Update a record. See blk_data.

// Post lender accept borrow proposal.
exports.ctr_contract_propose_accept_post = [

    // Validate fields
    body('book_id', 'book_id must not be empty.').isLength({ min: 1 }).trim(),
    body('contract_id', 'book_id must not be empty.').isLength({ min: 1 }).trim(),
    body('tx_addr', 'tx_addr must not be empty.').isLength({ min: 1 }).trim(),
    body('block_number', 'block_number must not be empty.').isLength({ min: 1 }).trim(),

    // Sanitize fields.
    sanitizeBody('*').escape(),
    // Process request after validation and sanitization.
    (req, res, next) => {

        // Extract the validation errors from a request.
        const errors = validationResult(req);
        if (!errors.isEmpty()) {
            // There are errors. Render form again with sanitized values/error messages.
            res.status(400).send({ errors: errors.array() });
            return;
        }

        // Create a Book object with escaped/trimmed data
        var book_fields =
            {
                _id: req.body.book_id, // This is required, or a new ID will be assigned!
                status: 'on_loan'
            };

        // Create a contract object with escaped/trimmed data
        var contract_fields = {
            $push: {
                blk_data: {
                    tx_addr: req.body.tx_addr,
                    block_number: req.body.block_number
                }
            }
        };

        async.parallel({
            //call the function get book model
            book: function(callback) {
                Book.findByIdAndUpdate(req.body.book_id, book_fields, {}).exec(callback);
            },
            contract: function(callback) {
                Contract.findByIdAndUpdate(req.body.contract_id, contract_fields, {}).exec(callback);
            },
        }, function(error, results) {
            if (error) {
                res.status(400).send({ errors: errors.array() });
                return;
            }

            if ((results.book.isNew) || (results.contract.isNew)) {
                res.status(400).send({ errors: errors.array() });
                return;
            }

            var resObj = {
                "res": results.contract.url
            };
            res.status(200).send(JSON.stringify(resObj));
        });
    },
];

Thanks for the replies.

I tried the first approach, but nothing changed. Then, I tried to log the results. I just drilled down level by level, until I finally got to where the data was being displayed.

After a while I found the problem: When I was sending the response, I was converting it to a string via .toString().

I fixed that and now it works brilliantly. Sorry for the false alarm.

You can declare an array as below

trk : [{
    lat : String,
    lng : String
}]

but it will set [] (empty array) as the default value and if you don't want this default value then to overwrite this default, you need to set the default value to undefined as below

trk: {
    type: [{
        lat : String,
        lng : String
    }],
    default: undefined
}