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<?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.
*
* For more details and usage information on Cache, see the [guide article on caching](guide:caching-overview).
*
* @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 bool 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 = [];
/**
* 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) {
$hash = $this->generateReusableHash();
if (!array_key_exists($hash, self::$_reusableData)) {
self::$_reusableData[$hash] = $this->generateDependencyData($cache);
}
$this->data = self::$_reusableData[$hash];
} else {
$this->data = $this->generateDependencyData($cache);
}
}
/**
* Returns a value indicating whether the dependency has changed.
* @deprecated since version 2.0.11. Will be removed in version 2.1. Use [[isChanged()]] instead.
*/
public function getHasChanged($cache)
{
return $this->isChanged($cache);
}
/**
* Checks whether the dependency is changed
* @param Cache $cache the cache component that is currently evaluating this dependency
* @return bool whether the dependency has changed.
* @since 2.0.11
*/
public function isChanged($cache)
{
if ($this->reusable) {
$hash = $this->generateReusableHash();
if (!array_key_exists($hash, self::$_reusableData)) {
self::$_reusableData[$hash] = $this->generateDependencyData($cache);
}
$data = self::$_reusableData[$hash];
} else {
$data = $this->generateDependencyData($cache);
}
return $data !== $this->data;
}
/**
* Resets all cached data for reusable dependencies.
*/
public static function resetReusableData()
{
self::$_reusableData = [];
}
/**
* Generates a unique hash that can be used for retrieving reusable dependency data.
* @return string a unique hash value for this cache dependency.
* @see reusable
*/
protected function generateReusableHash()
{
$data = $this->data;
$this->data = null; // https://github.com/yiisoft/yii2/issues/3052
$key = sha1(serialize($this));
$this->data = $data;
return $key;
}
/**
* Generates the data needed to determine if dependency is 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);
}
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