Storing a one to many relationship in Node.js using Mongoose

Question

I have a very simple one to many relationship where a User has a list of Alerts. For this, I've defined the following schemas:

var userSchema = new Schema({
    email: String,
    alerts: [{type: Schema.Types.ObjectId, ref: 'Alert'}]
});
var User = mongoose.model('User', userSchema);

var alertSchema = new Schema({
    _creator: {type: Schema.Types.ObjectId, ref: 'User'},
    value: String,
});
var Alert = mongoose.model('Alert', alertSchema);

Now, I'm trying to create a function which creates a new Alert and adds it to an existing User from the database. I have the following code (removing error-handling so the code is shorter):

function createAlertForUser(userId, value) {
    User.findOne({_id: userId}, function (error, user) {

        var alert = new Alert({
            _creator: userId,
            value: value
        });

        alert.save(function (error, alert) {

            // push it to the user
            user.alerts.push(alert);
            user.save(function(error) {
                console.log("saved");
            });
        });
    });
}

However, when I check the database, I seem to be saving null values to the User's list of alerts. Any ideas what I'm missing?

Answer 1

You try to push a whole Alert object to an array of ObjectId.

Try this instead:

user.alerts.push(alert.id);

or

user.alerts.push(alert._id);

both are correct.