Odoo V15 - How to set a line with an Onchange Function

Question

I have this calendar that is made with Javascript.

When you click in "Libre", a view opens, where you can create a reserve. I want the reservation line as default and look something like this. In this case I did it manually, and I want it to appear automatically. I know I need an on @api.onchange function.

The roomid field ("Room" in the image) has the ID of the room that I need to add in reservation.line. I get this from .js

I have something like this in my code and it's getting exactly the room I want, but I don't know how to make it appear automatically.

class HotelReservation(models.Model):
    _name = "hotel.reservation"
   
  room_id = fields.Many2one("hotel.room", string="Room", required=True)

  roomid= fields.Integer(related='room_id.id', string="Room")

  reservation_line = fields.One2many(
        "hotel.reservation.line",
        "line_id",
        string="Reservation Line",
        help="Hotel room reservation details.",
        readonly=True,
        states={"draft": [("readonly", False)]},
    )


   @api.onchange('roomid')
   def onchange_reservation_line(self):
        if self.roomid:
            room = self.env['hotel.room'].search([('id' ,'=', self.roomid)])
            # Some return here?

Answer 1

You can read in the write function documentation that the expected value of a One2many or Many2many relational field is a list of Command that manipulates the relation the implement. There are a total of 7 commands: create(), update(), delete(), unlink(), link(), clear(), and set().

roomid is related to room_id so you can use it in onchange function and avoid calling the search method to get the room record.

Example:

@api.onchange('room_id')
def onchange_reservation_line(self):
    if self.room_id:
        self.reservation_line = [
            Command.clear(),
            Command.create({
                'field_name': field_value,
                ...
            }),
        ]