I have a Many2one field which is linked to another model:

field_id = fields.Many2one(''model.name")

Then I use this, to make it related with a field.

related_field = fields.Integer(related="field_id.computed_field")

I also made the default of Many2one field by using this function:

def defaultm2o(self):
    return self.env['hotel.room'].search([], limit=1).id

Now, why my Many2one field won't give values to my related fields unless I specify it to xml?

and most importantly, how do I make it that I may not include it in xml file?