common\models\Address::beforeSave PHP Method

    public function beforeSave($insert)
    {
        if (parent::beforeSave($insert)) {
            if ($this->is_default == self::BOOL_TRUE) {
                // Update all adresses to non-default.
                static::updateAll(['is_default' => self::BOOL_FALSE], ['user_id' => $this->user_id]);
            }
            return true;
        } else {
            return false;
        }
    }