多筆紀錄的處理（Working With Multiple Records）

有時候，使用者一個動作會同時建立或者影響不同表格的紀錄。這一類操作最好要遵守 ACID （原子性、一致性性、隔離性、持久性）的特性。Yii2 supports transactions, isolation levels, and allow you to validate data independently.

比方說，要開始一場交易，你可能同時需要儲存交易參考資料與相關檔案。

public function actionCreate()
{
    $model = new Credit();
    $modelReferences = [new CreditRefence()];
    $modelFiles = [new CreditFile()];

    if (Yii::$app->request->isPost) {
        $model->load(Yii::$app->request->post());

        foreach (Yii::$app->requestPost($modelReferences[0]->formName())
            as $i => $data
        ) {
            $newModel = new CreditReference();
            $newModel->load($data, '');
            $modelReferences[$i] = $newModel;
        }

        foreach (Yii::$app->requestPost($modelFiles[0]->formName())
            as $i => $data
        ) {
            $newModel = new CreditFile();
            $newModel->load($data, '');
            $newModel->file = UploadedFile::getInstance($newModel, "[$i]file");
            $modelFiles[$i] = $newModel;
        }

        $transaction = Yii::$app->db->beginTransaction(
            Transaction::SERIALIZABLE
        );

        try {
            $valid = $model->validate();
            $valid = Model::validateMultiple($modelReferences, [
                    'name',
                    'last_name',
                    // other fields, make sure to NOT include credit_id since
                    // the record has not been created yet.
                ]) && $valid;
            $valid =  Model::validateMultiple($modelFiles, [
                    'file',
                    // other fields, make sure to NOT include credit_id since
                    // the record has not been created yet.
                ]) && $valid;

            if ($valid) {
                // 模型已經驗證過，所以這邊不再驗證
                $model->save(false);

                foreach ($modelReferences as $newModel) {
                    $newModel->credit_id = $model->id;
                    $newModel->save(false);
                }

                foreach ($modelFiles as $newModel) {
                    $newModel->credit_id = $model->id;
                    $newModel->file->saveAs(Yii::getAlias(
                        '@webroot/uploads/' . $model->file->name
                    ));
                    $newModel->save(false);
                }

                $transaction->commit();
                return $this->redirect(['credit/view', ['id' => $model->id]]);
            } else {
                //驗證失敗，交易取消
                $transaction->rollBack();
            }
        } catch (Exception $e) {
            //出現例外，交易取消
            $transaction->rollBack();
            throw new BadRequestHttpException($e->getMessage(), 0, $e);
        }
    }

    return $this->render('create', [
        'model' => $model,
        'modelReferences' => $modelReferences,
        'modelFiles' => $modelFiles,

    ]);
}

以下說明各個步驟：

1. 檢查輸入是否合法
   In this case we are assuming the controller already checked the user credentials using filter and at the action its enough to check if the petition is using thepostmethod.

2. 建立模型、輸入使用者資料
   雖然只有一筆交易，但是可能影響多個檔案與相關資料

3. 開始交易
   Its important to start the transaction at this point since some validations likeuniqueandexistmight be necessary so we start the transaction here to avoid [Reading Phenomena] (https://en.wikipedia.org/wiki/Isolation_(database_systems)#Read_phenomena](https://en.wikipedia.org/wiki/Isolation_(database_systems)#Isolation_levels))))))))\).

4. 驗證模型
   Its important to validate them all to show the user all the validation errors if necessary. Using anifstatement like this
   if ($model->validate() && Model::validateMultiple(...))
   Is simpler to understand but if the first validation fails the second one won't be executed.
   Also notice that we are not going to validatecredit_idon the files and references since the credit has not been created yet.

   1. 如果驗證失敗， end the transaction with arollBack()just in case any validation had updated anything
      The action will then render the view and if you are using something likeActiveFormthe user will see all the validation errors.

5. 如果交易驗證成功，我們就儲存所有相關的模型（model）
   We will save them without validation since they were already validated and assign thecredit_idto the files and references after the credit has been saved.

   1. Catch any exception from the validation or saving and execute rollBack()
      For debugging purposes we throw a new exception with the previous one so it can get caught by the Yii2 exception manager.

6. 如果沒有任何例外，就commit()改變的部份
   之後就執行交易成功後的行為，比方說導向其他頁面，或者更新頁面資訊。

1. Operations Triggered by Events

假設你有兩個模型：Credit 模型，包含id和amount兩個參數；還有一個CreditPayment模型，包含 credit_id和amount參數。 當你建立CreditPayment時，希望能同時更新Credit的amount：

class CreditPayment extends ActiveRecord
{
    public function afterSave($insert, $changedAttributes)
    {
        parent::afterSave($insert, $changedAttributes);
        if ($insert === false) {
            return; // only work with newly created payments
        }

        $this->credit->amount = $this->credit->amount - $this->ammount;
        if ($this->credit->amount <= 0) {
            $this->credit->status = Credit::STATUS_PAYMENT_FINISHED;
        }

        if ($this->credit->save(false) === false) {
            throw new Exception("credit couldn't be update");
        }
    }

    public function getCredit()
    {
        return $this->hasOne(Credit::className(), ['id' => 'credit_id']);
    }
}

如果出現任何例外（exception），payment 本身會被儲存，但是不影響credit的amount。

We can encapsulate all the operation on a transaction very simply using the methodyii\db\ActiveRecord::transactions()

public function transactions()
{
    return [
        self::SCENARIO_DEFAULT => self::OP_INSERT,
    ];
}