This is a nodejs / express MVC app. I've got a custom model called MyModel (not really, but for privacy, let's pretend that's the name). The properties of the class are set as null by default:

export class MyModel {

    /* ----- FIELDS ----- */
    protected _id: string = null;
    protected _name: string = null;
    ...

The constructor only sets the name property, all other properties are set by database triggers. So in my save method (which persists to the db), it works kind of like this:

    async save() {
        let client:PoolClient = null;
        try {
            client = await pool.connect();
            let query;
            if (this._id === null) {
                query = {
                    name: 'insertMyModel',
                    text: 'INSERT INTO my_model (name) VALUES ($1::text) RETURNING id',
                    values: [this._name],
                    rowMode: 'array',
                };

            } else {
                ...
            }

            const result = await client.query(query);
            if (this._id === null) {
                this._id = result.rows[0][0];
                ...

The controller, simply (for now) returns MyModel to string, which should show the returned id.

    public async new(req, res) {
        try {
            const mymodel = await MyModel.new(req.params.name);

            res.send(mymodel.toString());
        } catch (error) {
            res.status(400).send(error);
        }
    }

And (thank you @Barmar for noticing) I forgot to include MyModel's new function, so adding that here. This constructs the new MyModel instance and then calls save.

    public static async new(name: string) : Promise<GekModel> {
        if (name === undefined || name === null || (name = name.trim()) === '') {
            name = uniqueNamesGenerator();
        }

        const mymodel = new MyModel(name);
        mymodel.save();
        return mymodel;
    }

Using interactive debugging, I've determined that in the save method, indeed, the db is propertly returning the ID. And I've seen that in the save method, the returned id is assigned to the _id property. However, by the time I get back to the controller's new, the _id property is back to null. boink.

I assume this has something to do with the async nature of it? But, I'm at a loss. Would love any ideas!