def default_get(self, fields):
    result = super(PortalShare, self).default_get(fields)
    result['res_model'] = self._context.get('active_model', False)
    result['res_id'] = self._context.get('active_id', False)
    if result['res_model'] and result['res_id']:
        record = self.env[result['res_model']].browse(result['res_id'])
        result['share_link'] = record.get_base_url() + record._get_share_url(redirect=True)
    return result