If you explicitly declare _id: Schema.ObjectId for your model, then the ObjectId will not be available after new or save.

[totty90]

If you explicitly declare

_id: Schema.ObjectId

for your model, then the ObjectId will not be available after new or save.

[aheckmann]

please post code to reproduce.

[totty90]

Source: http://stackoverflow.com/questions/6074245/node-mongoose-get-last-inserted-id
But here is the code too:

var SerialSchema = new Schema({
     _id        : ObjectId
    ,serial     : String
    ,year       : Number
}, { strict: true
    ,toObject: {
      virtuals: true
    }
    ,toJSON: {
      virtuals: true
    }
});

var serial = new Serial({serial: 'abc', year: 2012});
serial.save(function(err, _serial){
    // no error
    // serial._id or serial.id is not defined
    // _serial._id or _serial.id is not defined too
})

[totty90]

"version": "3.4.0",

[aheckmann]

ah, the docs were incorrectly hiding the option you need (will be fixed next time they're published).

you must pass the auto option like so:

new Schema({ _id: { type: Schema.ObjectId, auto: true }})

[totty90]

thanks

[jeshuneo]

new Schema({ _id: { type: Schema.ObjectId, auto: true }})
"CHANGE (_id) to (id)"