Document not updated in findOneAndUpdate

Please add option in findOneAndUpdate - { new: true };

It matters what schema you use to query database

Discriminators build the mongo queries based on the object you use. For instance, If you enable debugging on mongo using mongoose.set('debug', true) and run Profile.findOneAndUpdate() you should see something like:

Mongoose: profiles.findAndModify({
  _id: ObjectId("5c78519e61f4b69da677a87a")
}, [], {
  '$set': {
    email: '[email protected]',
    city: 'New York',
    accountType: 'helper',
    username: 'User NAme', __v: 0 } }, { new: true, upsert: false, remove: false, projection: {} })

Notice it uses only the fields defined in Profile schema.

If you use Helper, you would get something like:

profiles.findAndModify({
  accountType: 'helper',
  _id: ObjectId("5c78519e61f4b69da677a87a")
}, [], {
  '$set': {
    jobTitle: 'CTO',
    email: '[email protected]',
    city: 'New York',
    accountType: 'helper ', 
    username: 'User Name', __v: 0 } }, { new: true, upsert: false, remove: false, projection: {} })

Notice it adds the discriminator field in the filter criteria, this is documented:

Discriminator models are special; they attach the discriminator key to queries. In other words, find(), count(), aggregate(), etc. are smart enough to account for discriminators.

So what you need to do when updating is to use the discriminator field in order to know which Schema to use when calling update statement:

app.put("/profile/:id", function(req, res){
console.log(req.body);

if(ObjectId.isValid(req.params.id)) {

  switch(req.body.accountType) {
    case 'helper':
    schema = Helper;
    break;
    case 'finder':
    schema = Finder;
    break;
    default:
    schema = Profile;
  }      

  schema.findOneAndUpdate({ _id: req.params.id }, { $set : req.body }, { new: true, upsert: false, remove: {}, fields: {} }, function(err, updatedProfile){
      if(err){
          console.log(err);
          res.json(err);
      } else {
          console.log(updatedProfile);
          res.json(updatedProfile);
      }

  });
} else {
  res.json({ error: "Invalid ObjectId"});
} });

Notice, above is not necessary when creating a new document, in that scenario mongoose is able to determine which discriminator to use.

You cannot update discriminator field

Above behavior has a side effect, you cannot update the discriminator field because it will not find the record. In this scenario, you would need to access the collection directly and update the document, as well as define what would happen with the fields that belong to the other discriminator.

db.profile.findOneAndUpdate({ _id: req.params.id }, { $set : req.body }, { new: true, upsert: false, remove: {}, fields: {} }, function(err, updatedProfile){
              if(err) {
                res.json(err);
              } else {
                console.log(updatedProfile);
                res.json(updatedProfile);      
              }
          });