Updating objects within array in MongoDB with mongoose

Question

I'm trying to update objects within an array in a document. The objects are not subdocuments and therefore don't have a unique ID. I've tried looking at various methods to do this but it just doesn't seem to have any effect (as in, nothing happens - no errors, but the document doesn't update.

Probably easier just to show the code. First, here's an example of a document in this collection:

{
    _id: 123,
    //other fields go here
    submissions: [
        {
            submission: 1,
            downloaded: null, //This should be an ISODate when populated
            assessor: null,   //This should be an ObjectID when populated
            feedbackUploaded: null, //This should also be an ISODate
            path: '401Test1.doc',
            assessorNotes: null //This should be a string when populated
        },
        {
            submission: 2,
            downloaded: null,
            assessor: null,
            feedbackUploaded: null,
            path: '401Test2.doc',
            assessorNotes: null
        }
    ]
}

And now my mongoose query (within an express route):

const unit = req.body.unit; //e.g. 123
const submission = req.body.submission // e.g. 2
const date = Date.now();

Unit.update({ "_id": unit, "submissions.submission": submission }, {
        $set: {
            'submissions.assessorNotes': req.body.assessorComments,
            'submissions.feedbackUploaded': date,
            'submissions.assessor': req.body.assessor
        }, function(err){
            //callback
        }
    })

I've also tried this using $ notation in the $set command i.e. 'submissions.$.assessorNotes': req.body.assessorComments' but this doesn't seem to work either.

Where am I going wrong?!

Cheers!

Chris

it should work with the positional operator $. are you sure you have a match? if you do just find with these params, do you find the document? — TomG
– TomG, Commented Oct 26, 2016 at 15:24
Tried running a find and it returned the correct document, so it looks as though I'm getting a match - it just isn't updating. Have tried with findOneAndUpdate as well - same problem — Chris
– Chris, Commented Oct 26, 2016 at 16:05

dyouberg · Accepted Answer · 2016-10-26 16:31:08Z

Just tested this with the positional operator as mentioned above by TomG in a shell.

> db.foo.find().pretty()
{
    "_id" : 123,
    "submissions" : [
        {
            "submission" : 1,
            "downloaded" : null,
            "assessor" : null,
            "feedbackUploaded" : null,
            "path" : "401Test1.doc",
            "assessorNotes" : null
        },
        {
            "submission" : 2,
            "downloaded" : null,
            "assessor" : null,
            "feedbackUploaded" : null,
            "path" : "401Test2.doc",
            "assessorNotes" : null
        }
    ]
}

Then I ran the update command:

db.foo.update(
  { _id: 123, "submissions.submission": 2 }, 
  { $set: {
    "submissions.$.assessorNotes": "testAssessorNotes",
    "submissions.$.feedbackUploaded": new Date(),
    "submissions.$.assessor": "testAssessor"
  } }
)

Results are as follows:

{
    "_id" : 123,
    "submissions" : [
        {
            "submission" : 1,
            "downloaded" : null,
            "assessor" : null,
            "feedbackUploaded" : null,
            "path" : "401Test1.doc",
            "assessorNotes" : null
        },
        {
            "submission" : 2,
            "downloaded" : null,
            "assessor" : "testAssessor",
            "feedbackUploaded" : ISODate("2016-10-26T15:33:09.573Z"),
            "path" : "401Test2.doc",
            "assessorNotes" : "testAssessorNotes"
        }
    ]
}

Edit: My hunch is that the error could also be with the update in Mongoose, you could try changing both to the positional operators, as well as using findOneAndUpdate if it fits your needs instead of update.

Please try this query for Mongoose:

Unit.update(
    { "_id": unit, "submissions.submission": submission }, 
    { $set: {
        'submissions.$.assessorNotes': req.body.assessorComments,
        'submissions.$.feedbackUploaded': date,
        'submissions.$.assessor': req.body.assessor
    } }, function(err, result) {
        //callback
    }
});

Just tried findOneAndUpdate and appear to have the same problem. When I do a find as Tom suggested, it returns the correct document so it looks as though I have a match. Is there another alternative to update and findOneAndUpdate? Perhaps using save or something similar?
You could use find/findOne to return your object in the callback, then modify the value and finally call the save function. Are you also using the positional operator in your $set ?
I added a query for Mongoose, can you please try that and see if it works? I noticed a missing brace at the end of your set command.
OK, I've managed to solve it - I'll add the solution shortly, but basically it involved doing a findById on the document, then looping through the submission array, looking for a match on submission and then using save - so similar to your suggestion. Very strange that update didn't work in the first place - is this a common bug with mongoose?
of course it will work with iterating and save, but it should work also with update and findOneAndUpdate and findByIdAndUpdate. Are you sure your req.body parameters are fine? do you get any error?

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