<?php /** * @link http://www.yiiframework.com/ * @copyright Copyright (c) 2008 Yii Software LLC * @license http://www.yiiframework.com/license/ */ namespace yii\caching; /** * Dependency is the base class for cache dependency classes. * * Child classes should override its [[generateDependencyData()]] for generating * the actual dependency data. * * @author Qiang Xue <qiang.xue@gmail.com> * @since 2.0 */ abstract class Dependency extends \yii\base\Object { /** * @var mixed the dependency data that is saved in cache and later is compared with the * latest dependency data. */ public $data; /** * @var boolean whether this dependency is reusable or not. True value means that dependent * data for this cache dependency will be generated only once per request. This allows you * to use the same cache dependency for multiple separate cache calls while generating the same * page without an overhead of re-evaluating dependency data each time. Defaults to false. */ public $reusable = false; /** * @var array static storage of cached data for reusable dependencies. */ private static $_reusableData = array(); /** * @var string a unique hash value for this cache dependency. */ private $_hash; /** * Evaluates the dependency by generating and saving the data related with dependency. * This method is invoked by cache before writing data into it. * @param Cache $cache the cache component that is currently evaluating this dependency */ public function evaluateDependency($cache) { if (!$this->reusable) { $this->data = $this->generateDependencyData($cache); } else { if ($this->_hash === null) { $this->_hash = sha1(serialize($this)); } if (!array_key_exists($this->_hash, self::$_reusableData)) { self::$_reusableData[$this->_hash] = $this->generateDependencyData($cache); } $this->data = self::$_reusableData[$this->_hash]; } } /** * Returns a value indicating whether the dependency has changed. * @param Cache $cache the cache component that is currently evaluating this dependency * @return boolean whether the dependency has changed. */ public function getHasChanged($cache) { if (!$this->reusable) { return $this->generateDependencyData($cache) !== $this->data; } else { if ($this->_hash === null) { $this->_hash = sha1(serialize($this)); } if (!array_key_exists($this->_hash, self::$_reusableData)) { self::$_reusableData[$this->_hash] = $this->generateDependencyData($cache); } return self::$_reusableData[$this->_hash] !== $this->data; } } /** * Resets all cached data for reusable dependencies. */ public static function resetReusableData() { self::$_reusableData = array(); } /** * Generates the data needed to determine if dependency has been changed. * Derived classes should override this method to generate the actual dependency data. * @param Cache $cache the cache component that is currently evaluating this dependency * @return mixed the data needed to determine if dependency has been changed. */ abstract protected function generateDependencyData($cache); }