Yii2 TimestampBehavior行为

 <?php
 /**
  * @link http://www.yiiframework.com/
  * @copyright Copyright (c) 2008 Yii Software LLC
  * @license http://www.yiiframework.com/license/
  */

 namespace yii\behaviors;

 use yii\base\InvalidCallException;
 use yii\db\BaseActiveRecord;

 /**
  * TimestampBehavior automatically fills the specified attributes with the current timestamp.
  *
  * To use TimestampBehavior, insert the following code to your ActiveRecord class:
  *
  * ```php
  * use yii\behaviors\TimestampBehavior;
  *
  * public function behaviors()
  * {
  *     return [
  *         TimestampBehavior::className(),
  *     ];
  * }
  * ```
  *
  * By default, TimestampBehavior will fill the `created_at` and `updated_at` attributes with the current timestamp
  * when the associated AR object is being inserted; it will fill the `updated_at` attribute
  * with the timestamp when the AR object is being updated. The timestamp value is obtained by `time()`.
  *
  * Because attribute values will be set automatically, it's a good idea to make sure `created_at` and `updated_at` aren't
  * in `rules()` method of the model.
  *
  * For the above implementation to work with MySQL database, please declare the columns(`created_at`, `updated_at`) as int(11) for being UNIX timestamp.
  *
  * If your attribute names are different or you want to use a different way of calculating the timestamp,
  * you may configure the [[createdAtAttribute]], [[updatedAtAttribute]] and [[value]] properties like the following:
  *
  * ```php
  * use yii\db\Expression;
  *
  * public function behaviors()
  * {
  *     return [
  *         [
  *             'class' => TimestampBehavior::className(),
  *             'createdAtAttribute' => 'create_time',
  *             'updatedAtAttribute' => 'update_time',
  *             'value' => new Expression('NOW()'),
  *         ],
  *     ];
  * }
  * ```
  *
  * In case you use an [[\yii\db\Expression]] object as in the example above, the attribute will not hold the timestamp value, but
  * the Expression object itself after the record has been saved. If you need the value from DB afterwards you should call
  * the [[\yii\db\ActiveRecord::refresh()|refresh()]] method of the record.
  *
  * TimestampBehavior also provides a method named [[touch()]] that allows you to assign the current
  * timestamp to the specified attribute(s) and save them to the database. For example,
  *
  * ```php
  * $model->touch('creation_time');
  * ```
  *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @author Alexander Kochetov <creocoder@gmail.com>
  * @since 2.0
  */
 class TimestampBehavior extends AttributeBehavior
 {
     /**
      * @var string the attribute that will receive timestamp value
      * Set this property to false if you do not want to record the creation time.
      */
     public $createdAtAttribute = 'created_at';
     /**
      * @var string the attribute that will receive timestamp value.
      * Set this property to false if you do not want to record the update time.
      */
     public $updatedAtAttribute = 'updated_at';
     /**
      * @inheritdoc
      *
      * In case, when the value is `null`, the result of the PHP function [time()](http://php.net/manual/en/function.time.php)
      * will be used as value.
      */
     public $value;

     /**
      * @inheritdoc
      */
     public function init()
     {
         parent::init();

         if (empty($this->attributes)) {
             $this->attributes = [
                 BaseActiveRecord::EVENT_BEFORE_INSERT => [$this->createdAtAttribute, $this->updatedAtAttribute],
                 BaseActiveRecord::EVENT_BEFORE_UPDATE => $this->updatedAtAttribute,
             ];
         }
     }

     /**
      * @inheritdoc
      *
      * In case, when the [[value]] is `null`, the result of the PHP function [time()](http://php.net/manual/en/function.time.php)
      * will be used as value.
      */
     protected function getValue($event)
     {
         if ($this->value === null) {
             returntime();
         }
         return parent::getValue($event);
     }

     /**
      * Updates a timestamp attribute to the current timestamp.
      *
      * ```php
      * $model->touch('lastVisit');
      * ```
      * @param string $attribute the name of the attribute to update.
      * @throws InvalidCallException if owner is a new record (since version 2.0.6).
      */
     public function touch($attribute)
     {
         /* @var $owner BaseActiveRecord */
         $owner = $this->owner;
         if ($owner->getIsNewRecord()) {
             throw new InvalidCallException('Updating the timestamp is not possible on a new record.');
         }
         $owner->updateAttributes(array_fill_keys((array) $attribute, $this->getValue(null)));
     }
 }

TimestampBehavior 里面的public function init(){}初始化绑定事件处理的方法数据

 /**
      * @inheritdoc
      */
     public function init()
     {
         parent::init();

         if (empty($this->attributes)) {
             $this->attributes = [
                 BaseActiveRecord::EVENT_BEFORE_INSERT => [$this->createdAtAttribute, $this->updatedAtAttribute],
                 BaseActiveRecord::EVENT_BEFORE_UPDATE => $this->updatedAtAttribute,
             ];
         }
     }

TimestampBehavior 父级AttributeBehavior 里面events()方法  为事件绑定执行handle :evaluateAttributes方法

 /**
      * @inheritdoc
      */
     public function events()
     {
         return array_fill_keys(
             array_keys($this->attributes),
             'evaluateAttributes'
         );
     }

事件绑定的方法：evaluateAttributes方法，

  /**
      * Evaluates the attribute value and assigns it to the current attributes.
      * @param Event $event
      */
     public function evaluateAttributes($event)
     {
         if ($this->skipUpdateOnClean
             && $event->name == ActiveRecord::EVENT_BEFORE_UPDATE
             && empty($this->owner->dirtyAttributes)
         ) {
             return;
         }

         if (!empty($this->attributes[$event->name])) {
             $attributes = (array) $this->attributes[$event->name];
             $value = $this->getValue($event);
             foreach ($attributes as $attribute) {
                 // ignore attribute names which are not string (e.g. when set by TimestampBehavior::updatedAtAttribute)
                 if (is_string($attribute)) {
                     $this->owner->$attribute = $value;
                 }
             }
         }
     }

当update 或者insert  save数据时候，BaseActiveRecord.php 里面的save()：

 /**
      * Saves the current record.
      *
      * This method will call [[insert()]] when [[isNewRecord]] is true, or [[update()]]
      * when [[isNewRecord]] is false.
      *
      * For example, to save a customer record:
      *
      * ```php
      * $customer = new Customer; // or $customer = Customer::findOne($id);
      * $customer->name = $name;
      * $customer->email = $email;
      * $customer->save();
      * ```
      *
      * @param boolean $runValidation whether to perform validation (calling [[validate()]])
      * before saving the record. Defaults to `true`. If the validation fails, the record
      * will not be saved to the database and this method will return `false`.
      * @param array $attributeNames list of attribute names that need to be saved. Defaults to null,
      * meaning all attributes that are loaded from DB will be saved.
      * @return boolean whether the saving succeeded (i.e. no validation errors occurred).
      */
     public function save($runValidation = true, $attributeNames = null)
     {
         if ($this->getIsNewRecord()) {
             return $this->insert($runValidation, $attributeNames);
         } else {
             return $this->update($runValidation, $attributeNames) !== false;
         }
     }

调用ActiveRecord.php 里面的insert()  和update  ():

  public function insert($runValidation = true, $attributes = null)
     {
         if ($runValidation && !$this->validate($attributes)) {
             Yii::info('Model not inserted due to validation error.', __METHOD__);
             return false;
         }

         if (!$this->isTransactional(self::OP_INSERT)) {
             return $this->insertInternal($attributes);
         }

         $transaction = static::getDb()->beginTransaction();
         try {
             $result = $this->insertInternal($attributes);
             if ($result === false) {
                 $transaction->rollBack();
             } else {
                 $transaction->commit();
             }
             return $result;
         } catch (\Exception $e) {
             $transaction->rollBack();
             throw $e;
         }
     }
 public function update($runValidation = true, $attributeNames = null)
     {
         if ($runValidation && !$this->validate($attributeNames)) {
             Yii::info('Model not updated due to validation error.', __METHOD__);
             return false;
         }

         if (!$this->isTransactional(self::OP_UPDATE)) {
             return $this->updateInternal($attributeNames);
         }

         $transaction = static::getDb()->beginTransaction();
         try {
             $result = $this->updateInternal($attributeNames);
             if ($result === false) {
                 $transaction->rollBack();
             } else {
                 $transaction->commit();
             }
             return $result;
         } catch (\Exception $e) {
             $transaction->rollBack();
             throw $e;
         }
     }

调用ActiveRecord.php 里面insertInternal() 和updateInternal()：

 /**
      * Inserts an ActiveRecord into DB without considering transaction.
      * @param array $attributes list of attributes that need to be saved. Defaults to null,
      * meaning all attributes that are loaded from DB will be saved.
      * @return boolean whether the record is inserted successfully.
      */
     protected function insertInternal($attributes = null)
     {
         if (!$this->beforeSave(true)) {
             return false;
         }
         $values = $this->getDirtyAttributes($attributes);
         if (($primaryKeys = static::getDb()->schema->insert(static::tableName(), $values)) === false) {
             return false;
         }
         foreach ($primaryKeys as $name => $value) {
             $id = static::getTableSchema()->columns[$name]->phpTypecast($value);
             $this->setAttribute($name, $id);
             $values[$name] = $id;
         }

         $changedAttributes = array_fill_keys(array_keys($values), null);
         $this->setOldAttributes($values);
         $this->afterSave(true, $changedAttributes);

         return true;
     }
  /**
      * @see update()
      * @param array $attributes attributes to update
      * @return integer number of rows updated
      * @throws StaleObjectException
      */
     protected function updateInternal($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;
     }

调用BaseActiveRecord.php 里面的beforeSave(),触发$this->trigger($insert ? self::EVENT_BEFORE_INSERT : self::EVENT_BEFORE_UPDATE, $event)事件执行添加之前绑定的事件方法evaluateAttributes自动相关添加属性值:

  public function beforeSave($insert)
     {
         $event = new ModelEvent;
         $this->trigger($insert ? self::EVENT_BEFORE_INSERT : self::EVENT_BEFORE_UPDATE, $event);

         return $event->isValid;
     }

}