Hi, 

I would like to copy and create my own new sale.order model and save data into a separate table in database. Therefore, I am using '_inherit' with '_name' in new model.

However, sale.order also include sale.order.line then I create my own new 'sale.order.line' as above.

When I tried to click Save button, I got the error below: 

-> raise TypeError("Mixing apples and oranges: %s - %s" % (self, other))

Here is my source code

class MyOrder(models.Model):
    _name = "my.order"
    _inherit = 'sale.order'
    _description = "Sale Order"

    order_line = fields.One2many('my.order.line', 'order_id', string='Order Lines',
                                 states={'cancel': [('readonly', True)], 'done': [('readonly', True)]}, copy=True,
                                 auto_join=True)
    state = fields.Selection([
        ('draft', 'Draft'),
        ('sale', 'Sales Order'),
        ('done', 'Locked'),
        ('cancel', 'Cancelled'),
    ], string='Status', readonly=True, copy=False, index=True, track_visibility='onchange', track_sequence=3,
        default='draft')

    @api.model_cr
    def init(self):
        self._cr.execute("""
            ALTER TABLE public.my_order ALTER COLUMN warehouse_id DROP NOT NULL;
            ALTER TABLE public.my_order ALTER COLUMN picking_policy DROP NOT NULL;
            ALTER TABLE public.my_order ALTER COLUMN partner_invoice_id DROP NOT NULL;
            ALTER TABLE public.my_order ALTER COLUMN partner_shipping_id DROP NOT NULL;
            ALTER TABLE public.my_order ALTER COLUMN team_group DROP NOT NULL;
        """)

    @api.model
    def create(self, vals):
        if vals.get('name', _('New')) == _('New'):
            if 'company_id' in vals:
                vals['name'] = self.env['ir.sequence'].with_context(force_company=vals['company_id']).next_by_code(
                    'my.order') or _('New')
            else:
                vals['name'] = self.env['ir.sequence'].next_by_code('my.order') or _('New')

        # Makes sure 'pricelist_id' are defined
        if any(f not in vals for f in ['pricelist_id']):
            partner = self.env['res.partner'].browse(vals.get('partner_id'))
            vals['pricelist_id'] = vals.setdefault('pricelist_id',
                                                   partner.property_product_pricelist and partner.property_product_pricelist.id)
        # Change state of order to 'sale'
        vals['state'] = 'sale'
        vals['date_order'] = fields.Date.today()
        return super(MyOrder, self).create(vals)

​

class MyOrderLine(models.Model):
    _name = 'my.order.line'
    _inherit = 'sale.order.line'
    _description = 'Sales Order Line'

    order_id = fields.Many2one('my.order', string='Order Reference', required=True, ondelete='cascade',
                                  index=True,
                                  copy=False)

    state = fields.Selection([
        ('draft', 'Draft'),
        ('sale', 'Sales Order'),
        ('done', 'Done'),
        ('cancel', 'Cancelled'),
    ], related='order_id.state', string='Order Status', readonly=True, copy=False, store=True, default='draft')

    @api.model_cr
    def init(self):
        self._cr.execute("""
                ALTER TABLE public.my_order_line ALTER COLUMN customer_lead DROP NOT NULL;
            """)

    # Override for non-checking inventory
    @api.onchange('product_uom_qty')
    def _onchange_product_uom_qty(self):
        return {}

    # Override for non-checking inventory
    @api.onchange('product_uom_qty', 'product_uom', 'route_id')
    def _onchange_product_id_check_availability(self):
        return {}

Thank you for your help!