源码参考yii\db\baseActiveRecord

protected function updateInternal($attributes = null)
    {
        if (!$this->beforeSave(false)) {
            return false;
        }
        $values = $this->getDirtyAttributes($attributes);
        if (empty($values)) {
            $this->afterSave(false, $values);
            return 0;
        }
        $condition = $this->getOldPrimaryKey(true);
        $lock = $this->optimisticLock();
        if ($lock !== null) {
            $values[$lock] = $this->$lock + 1;
            $condition[$lock] = $this->$lock;
        }
        // We do not check the return value of updateAll() because it's possible
        // that the UPDATE statement doesn't change anything and thus returns 0.
        $rows = static::updateAll($values, $condition);

        if ($lock !== null && !$rows) {
            throw new StaleObjectException('The object being updated is outdated.');
        }

        if (isset($values[$lock])) {
            $this->$lock = $values[$lock];
        }

        $changedAttributes = [];
        foreach ($values as $name => $value) {
            $changedAttributes[$name] = isset($this->_oldAttributes[$name]) ? $this->_oldAttributes[$name] : null;
            $this->_oldAttributes[$name] = $value;
        }
        $this->afterSave(false, $changedAttributes);

        return $rows;
    }

$insert 表示是否是插入，changedAttributes显而易见可以知道，更新的时候被改变的attribute

呵呵

$insert 表示是否是插入，$changedAttributes 表示修改的字段

其实Yii2中登陆login本来就已经有事件了.Yii::$app->user->login($user);登陆成功会调用afterLogin方法,触发EVENT_AFTER_LOGIN

protected function afterLogin($identity, $cookieBased, $duration)
    {
        $this->trigger(self::EVENT_AFTER_LOGIN, new UserEvent([
            'identity' => $identity,
            'cookieBased' => $cookieBased,
            'duration' => $duration,
        ]));
    }

返回了完整的用户信息.所以事件没必要新增,UserLoginEvent也不需要了.