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CCache

Package	system.caching
Inheritance	abstract class CCache » CApplicationComponent » CComponent
Implements	IApplicationComponent, ICache, ArrayAccess
Subclasses	CApcCache, CDbCache, CEAcceleratorCache, CFileCache, CMemCache, CXCache, CZendDataCache
Since	1.0
Version	$Id$
Source Code	framework/caching/CCache.php

CCache is the base class for cache classes with different cache storage implementation.

A data item can be stored in cache by calling set and be retrieved back later by get. In both operations, a key identifying the data item is required. An expiration time and/or a dependency can also be specified when calling set. If the data item expires or the dependency changes, calling get will not return back the data item.

Note, by definition, cache does not ensure the existence of a value even if it does not expire. Cache is not meant to be a persistent storage.

CCache implements the interface ICache with the following methods:

get : retrieve the value with a key (if any) from cache
set : store the value with a key into cache
add : store the value only if cache does not have this key
delete : delete the value with the specified key from cache
flush : delete all values from cache

Child classes must implement the following methods:

CCache also implements ArrayAccess so that it can be used like an array.

Public Properties

Hide inherited properties

Property	Type	Description	Defined By
behaviors	array	the behaviors that should be attached to this component.	CApplicationComponent
isInitialized	boolean	whether this application component has been initialized (i.e., init() is invoked.	CApplicationComponent
keyPrefix	string	a string prefixed to every cache key so that it is unique.	CCache

Public Methods

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Method	Description	Defined By
__call()	Calls the named method which is not a class method.	CComponent
__get()	Returns a property value, an event handler list or a behavior based on its name.	CComponent
__isset()	Checks if a property value is null.	CComponent
__set()	Sets value of a component property.	CComponent
__unset()	Sets a component property to be null.	CComponent
add()	Stores a value identified by a key into cache if the cache does not contain this key.	CCache
asa()	Returns the named behavior object.	CComponent
attachBehavior()	Attaches a behavior to this component.	CComponent
attachBehaviors()	Attaches a list of behaviors to the component.	CComponent
attachEventHandler()	Attaches an event handler to an event.	CComponent
canGetProperty()	Determines whether a property can be read.	CComponent
canSetProperty()	Determines whether a property can be set.	CComponent
delete()	Deletes a value with the specified key from cache	CCache
detachBehavior()	Detaches a behavior from the component.	CComponent
detachBehaviors()	Detaches all behaviors from the component.	CComponent
detachEventHandler()	Detaches an existing event handler.	CComponent
disableBehavior()	Disables an attached behavior.	CComponent
disableBehaviors()	Disables all behaviors attached to this component.	CComponent
enableBehavior()	Enables an attached behavior.	CComponent
enableBehaviors()	Enables all behaviors attached to this component.	CComponent
flush()	Deletes all values from cache.	CCache
get()	Retrieves a value from cache with a specified key.	CCache
getEventHandlers()	Returns the list of attached event handlers for an event.	CComponent
getIsInitialized()	Checks whether this application component has been initialized (i.e., init() is invoked.)	CApplicationComponent
hasEvent()	Determines whether an event is defined.	CComponent
hasEventHandler()	Checks whether the named event has attached handlers.	CComponent
hasProperty()	Determines whether a property is defined.	CComponent
init()	Initializes the application component.	CCache
mget()	Retrieves multiple values from cache with the specified keys.	CCache
offsetExists()	Returns whether there is a cache entry with a specified key.	CCache
offsetGet()	Retrieves the value from cache with a specified key.	CCache
offsetSet()	Stores the value identified by a key into cache.	CCache
offsetUnset()	Deletes the value with the specified key from cache	CCache
raiseEvent()	Raises an event.	CComponent
set()	Stores a value identified by a key into cache.	CCache

Protected Methods

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Method	Description	Defined By
addValue()	Stores a value identified by a key into cache if the cache does not contain this key.	CCache
deleteValue()	Deletes a value with the specified key from cache	CCache
generateUniqueKey()		CCache
getValue()	Retrieves a value from cache with a specified key.	CCache
getValues()	Retrieves multiple values from cache with the specified keys.	CCache
setValue()	Stores a value identified by a key in cache.	CCache

Property Details

keyPrefix property

public string $keyPrefix;

a string prefixed to every cache key so that it is unique. Defaults to application ID.

Method Details

add() method

public boolean add(string $id, mixed $value, integer $expire=0, ICacheDependency $dependency=NULL)
$id	string	the key identifying the value to be cached
$value	mixed	the value to be cached
$expire	integer	the number of seconds in which the cached value will expire. 0 means never expire.
$dependency	ICacheDependency	dependency of the cached item. If the dependency changes, the item is labeled invalid.
{return}	boolean	true if the value is successfully stored into cache, false otherwise

Source Code: framework/caching/CCache.php#160 (show)


public function add($id,$value,$expire=0,$dependency=null)
{
    Yii::trace('Adding "'.$id.'" to cache','system.caching.'.get_class($this));
    if($dependency!==null)
        $dependency->evaluateDependency();
    $data=array($value,$dependency);
    return $this->addValue($this->generateUniqueKey($id),serialize($data),$expire);
}

Stores a value identified by a key into cache if the cache does not contain this key. Nothing will be done if the cache already contains the key.

addValue() method

protected boolean addValue(string $key, string $value, integer $expire)
$key	string	the key identifying the value to be cached
$value	string	the value to be cached
$expire	integer	the number of seconds in which the cached value will expire. 0 means never expire.
{return}	boolean	true if the value is successfully stored into cache, false otherwise

Source Code: framework/caching/CCache.php#256 (show)


protected function addValue($key,$value,$expire)
{
    throw new CException(Yii::t('yii','{className} does not support add() functionality.',
        array('{className}'=>get_class($this))));
}

Stores a value identified by a key into cache if the cache does not contain this key. This method should be implemented by child classes to store the data in specific cache storage. The uniqueness and dependency are handled in add() already. So only the implementation of data storage is needed.

delete() method

public boolean delete(string $id)
$id	string	the key of the value to be deleted
{return}	boolean	if no error happens during deletion

Source Code: framework/caching/CCache.php#174 (show)


public function delete($id)
{
    Yii::trace('Deleting "'.$id.'" to cache','system.caching.'.get_class($this));
    return $this->deleteValue($this->generateUniqueKey($id));
}

Deletes a value with the specified key from cache

deleteValue() method

protected boolean deleteValue(string $key)
$key	string	the key of the value to be deleted
{return}	boolean	if no error happens during deletion

Source Code: framework/caching/CCache.php#268 (show)


protected function deleteValue($key)
{
    throw new CException(Yii::t('yii','{className} does not support delete() functionality.',
        array('{className}'=>get_class($this))));
}

Deletes a value with the specified key from cache This method should be implemented by child classes to delete the data from actual cache storage.

flush() method

public void flush()

Source Code: framework/caching/CCache.php#186 (show)


public function flush()
{
    Yii::trace('Flushign cache','system.caching.'.get_class($this));
    throw new CException(Yii::t('yii','{className} does not support flush() functionality.',
        array('{className}'=>get_class($this))));
}

Deletes all values from cache. Be careful of performing this operation if the cache is shared by multiple applications. Child classes may implement this method to realize the flush operation.

generateUniqueKey() method

protected sring generateUniqueKey(string $key)
$key	string	a key identifying a value to be cached
{return}	sring	a key generated from the provided key which ensures the uniqueness across applications

Source Code: framework/caching/CCache.php#70 (show)


protected function generateUniqueKey($key)
{
    return md5($this->keyPrefix.$key);
}

get() method

public mixed get(string $id)
$id	string	a key identifying the cached value
{return}	mixed	the value stored in cache, false if the value is not in the cache, expired or the dependency has changed.

Source Code: framework/caching/CCache.php#80 (show)


public function get($id)
{
    if(($value=$this->getValue($this->generateUniqueKey($id)))!==false)
    {
        $data=unserialize($value);
        if(!is_array($data))
            return false;
        if(!($data[1] instanceof ICacheDependency) || !$data[1]->getHasChanged())
        {
            Yii::trace('Serving "'.$id.'" from cache','system.caching.'.get_class($this));
            return $data[0];
        }
    }
    return false;
}

Retrieves a value from cache with a specified key.

getValue() method

protected string getValue(string $key)
$key	string	a unique key identifying the cached value
{return}	string	the value stored in cache, false if the value is not in the cache or expired.

Source Code: framework/caching/CCache.php#202 (show)


protected function getValue($key)
{
    throw new CException(Yii::t('yii','{className} does not support get() functionality.',
        array('{className}'=>get_class($this))));
}

Retrieves a value from cache with a specified key. This method should be implemented by child classes to retrieve the data from specific cache storage. The uniqueness and dependency are handled in get() already. So only the implementation of data retrieval is needed.

getValues() method (available since v1.0.8)

protected array getValues(array $keys)
$keys	array	a list of keys identifying the cached values
{return}	array	a list of cached values indexed by the keys

Source Code: framework/caching/CCache.php#218 (show)


protected function getValues($keys)
{
    $results=array();
    foreach($keys as $key)
        $results[$key]=$this->getValue($key);
    return $results;
}

Retrieves multiple values from cache with the specified keys. The default implementation simply calls getValue multiple times to retrieve the cached values one by one. If the underlying cache storage supports multiget, this method should be overridden to exploit that feature.

init() method

public void init()

Source Code: framework/caching/CCache.php#59 (show)


public function init()
{
    parent::init();
    if($this->keyPrefix===null)
        $this->keyPrefix=Yii::app()->getId();
}

Initializes the application component. This method overrides the parent implementation by setting default cache key prefix.

mget() method (available since v1.0.8)

public array mget(array $ids)
$ids	array	list of keys identifying the cached values
{return}	array	list of cached values corresponding to the specified keys. The array is returned in terms of (key,value) pairs. If a value is not cached or expired, the corresponding array value will be false.

Source Code: framework/caching/CCache.php#107 (show)


public function mget($ids)
{
    $uniqueIDs=array();
    $results=array();
    foreach($ids as $id)
    {
        $uniqueIDs[$id]=$this->generateUniqueKey($id);
        $results[$id]=false;
    }
    $values=$this->getValues($uniqueIDs);
    foreach($uniqueIDs as $id=>$uniqueID)
    {
        if(!isset($values[$uniqueID]))
            continue;
        $data=unserialize($values[$uniqueID]);
        if(is_array($data) && (!($data[1] instanceof ICacheDependency) || !$data[1]->getHasChanged()))
        {
            Yii::trace('Serving "'.$id.'" from cache','system.caching.'.get_class($this));
            $results[$id]=$data[0];
        }
    }
    return $results;
}

Retrieves multiple values from cache with the specified keys. Some caches (such as memcache, apc) allow retrieving multiple cached values at one time, which may improve the performance since it reduces the communication cost. In case a cache doesn't support this feature natively, it will be simulated by this method.

offsetExists() method

public boolean offsetExists(string $id)
$id	string	a key identifying the cached value
{return}	boolean

Source Code: framework/caching/CCache.php#280 (show)


public function offsetExists($id)
{
    return $this->get($id)!==false;
}

Returns whether there is a cache entry with a specified key. This method is required by the interface ArrayAccess.

offsetGet() method

public mixed offsetGet(string $id)
$id	string	a key identifying the cached value
{return}	mixed	the value stored in cache, false if the value is not in the cache or expired.

Source Code: framework/caching/CCache.php#291 (show)


public function offsetGet($id)
{
    return $this->get($id);
}

Retrieves the value from cache with a specified key. This method is required by the interface ArrayAccess.

offsetSet() method

public void offsetSet(string $id, mixed $value)
$id	string	the key identifying the value to be cached
$value	mixed	the value to be cached

Source Code: framework/caching/CCache.php#304 (show)


public function offsetSet($id, $value)
{
    $this->set($id, $value);
}

Stores the value identified by a key into cache. If the cache already contains such a key, the existing value will be replaced with the new ones. To add expiration and dependencies, use the set() method. This method is required by the interface ArrayAccess.

offsetUnset() method

public boolean offsetUnset(string $id)
$id	string	the key of the value to be deleted
{return}	boolean	if no error happens during deletion

Source Code: framework/caching/CCache.php#315 (show)


public function offsetUnset($id)
{
    $this->delete($id);
}

Deletes the value with the specified key from cache This method is required by the interface ArrayAccess.

set() method

public boolean set(string $id, mixed $value, integer $expire=0, ICacheDependency $dependency=NULL)
$id	string	the key identifying the value to be cached
$value	mixed	the value to be cached
$expire	integer	the number of seconds in which the cached value will expire. 0 means never expire.
$dependency	ICacheDependency	dependency of the cached item. If the dependency changes, the item is labeled invalid.
{return}	boolean	true if the value is successfully stored into cache, false otherwise

Source Code: framework/caching/CCache.php#142 (show)


public function set($id,$value,$expire=0,$dependency=null)
{
    Yii::trace('Saving "'.$id.'" to cache','system.caching.'.get_class($this));
    if($dependency!==null)
        $dependency->evaluateDependency();
    $data=array($value,$dependency);
    return $this->setValue($this->generateUniqueKey($id),serialize($data),$expire);
}

Stores a value identified by a key into cache. If the cache already contains such a key, the existing value and expiration time will be replaced with the new ones.

setValue() method

protected boolean setValue(string $key, string $value, integer $expire)
$key	string	the key identifying the value to be cached
$value	string	the value to be cached
$expire	integer	the number of seconds in which the cached value will expire. 0 means never expire.
{return}	boolean	true if the value is successfully stored into cache, false otherwise

Source Code: framework/caching/CCache.php#238 (show)


protected function setValue($key,$value,$expire)
{
    throw new CException(Yii::t('yii','{className} does not support set() functionality.',
        array('{className}'=>get_class($this))));
}

Stores a value identified by a key in cache. This method should be implemented by child classes to store the data in specific cache storage. The uniqueness and dependency are handled in set() already. So only the implementation of data storage is needed.