One2one field in odoo

Odoo ORM doesn’t support One2one fields, but you can do them manually. In the example below we make one2one relationship between models fleet.vehicle and account.asset.asset.

In short, you set normal Many2one field (vehicle_id in the example) in a one model (doesn’t really matter which of the models you choose) and corresponding One2many field (asset_ids in the example) in another model. Then we add virtual Many2one field (asset_id in the example) with attributes compute and inverse.

class Fleet(models.Model):

_inherit = 'fleet.vehicle'
asset_id = fields.Many2one('account.asset.asset', compute='compute_asset', inverse='asset_inverse')
asset_ids = fields.One2many('account.asset.asset', 'vehicle_id')
def compute_asset(self):
    if len(self.asset_ids) > 0:
        self.asset_id = self.asset_ids[0]
def asset_inverse(self):
    if len(self.asset_ids) > 0:
        # delete previous reference
        asset = self.env['account.asset.asset'].browse(self.asset_ids[0].id)
        asset.vehicle_id = False
    # set new reference
    self.asset_id.vehicle_id = self

class Asset(models.Model):
_inherit = 'account.asset.asset'

vehicle_id = fields.Many2one('fleet.vehicle', string='Vehicle')

TODO: replace to @api.multi