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<?php
/**
* @link http://www.yiiframework.com/
* @copyright Copyright (c) 2008 Yii Software LLC
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* @license http://www.yiiframework.com/license/
*/
namespace yii\caching;
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/**
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* Dependency is the base class for cache dependency classes.
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*
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* Child classes should override its [[generateDependencyData()]] for generating
* the actual dependency data.
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*
* @property boolean $hasChanged Whether the dependency has changed.
*
* @author Qiang Xue <qiang.xue@gmail.com>
* @since 2.0
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*/
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abstract class Dependency extends \yii\base\Object
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{
/**
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* @var mixed the dependency data that is saved in cache and later is compared with the
* latest dependency data.
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*/
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public $data;
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/**
* Evaluates the dependency by generating and saving the data related with dependency.
* This method is invoked by cache before writing data into it.
*/
public function evaluateDependency()
{
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$this->data = $this->generateDependencyData();
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}
/**
* @return boolean whether the dependency has changed.
*/
public function getHasChanged()
{
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return $this->generateDependencyData() !== $this->data;
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}
/**
* Generates the data needed to determine if dependency has been changed.
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* Derived classes should override this method to generate the actual dependency data.
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* @return mixed the data needed to determine if dependency has been changed.
*/
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abstract protected function generateDependencyData();
}