odoo-contact-addons/partner_contact_majority/models/res_country_state.py

# -*- coding: utf-8 -*-
# License LGPL-3.0 or later (http://www.gnu.org/licenses/lgpl.html).
from odoo import fields, models, api


class ResCountryState(models.Model):
    _inherit = "res.country.state"

    majority_age = fields.Integer(
        string="Majority age",
        compute="_get_country_age",
        inverse="_set_standalone_age",
        store=True,
        readonly=False,
    )
    same_country_age = fields.Boolean(
        string="Same age as country",
        default=True,
    )

    @api.depends("country_id", "country_id.majority_age")
    def _get_country_age(self):
        for state in self.filtered("same_country_age"):
            state.majority_age = state.country_id.majority_age

    def _set_standalone_age(self):
        for state in self:
            state.same_country_age = False