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CacheInterface是缓存的基本接口。
数据项可以通过调用set（）存储在缓存中，并通过get（）稍后（在相同或不同的请求中）检索回来。在这两个操作中，都需要一个标识数据项的密钥。调用set（）时也可以指定到期时间和/或依赖项。如果数据项到期或者在调用get（）时依赖关系发生更改，则缓存将不返回任何数据。
缓存的典型使用模式如下:
$key = 'demo';
$data = $cache->get($key);
if ($data === false) {
// ...generate $data here...
$cache->set($key, $data, $duration, $dependency);
}因为CacheInterface扩展了ArrayAccess接口，所以它可以像数组一样使用。例如，
$cache['foo'] = 'some data';
echo $cache['foo'];下面我们看下其源码：
<?php
/**
* @link http://www.yiiframework.com/
* @copyright Copyright (c) 2008 Yii Software LLC
* @license http://www.yiiframework.com/license/
*/
namespace yii\caching;
/**
* CacheInterface is the base interface for cache.
*
* A data item can be stored in the cache by calling [[set()]] and be retrieved back
* later (in the same or different request) by [[get()]]. In both operations,
* a key identifying the data item is required. An expiration time and/or a [[Dependency|dependency]]
* can also be specified when calling [[set()]]. If the data item expires or the dependency
* changes at the time of calling [[get()]], the cache will return no data.
*
* A typical usage pattern of cache is like the following:
*
* ```php
* $key = 'demo';
* $data = $cache->get($key);
* if ($data === false) {
* // ...generate $data here...
* $cache->set($key, $data, $duration, $dependency);
* }
* ```
*
* Because CacheInterface extends the [[\ArrayAccess]] interface, it can be used like an array. For example,
*
* ```php
* $cache['foo'] = 'some data';
* echo $cache['foo'];
* ```
*
* For more details and usage information on Cache, see the [guide article on caching](guide:caching-overview).
*
* @author Qiang Xue <[email protected]>
* @author Dmitry Naumenko <[email protected]>
* @since 2.0.13. Previous framework versions used abstract class [[yii\caching\Cache]] as interface.
*/
interface CacheInterface extends \ArrayAccess
{
/**
* Builds a normalized cache key from a given key.
*
* If the given key is a string containing alphanumeric characters only and no more than 32 characters,
* then the key will be returned back prefixed with [[keyPrefix]]. Otherwise, a normalized key
* is generated by serializing the given key, applying MD5 hashing, and prefixing with [[keyPrefix]].
*
* @param mixed $key the key to be normalized
* @return string the generated cache key
*/
public function buildKey($key);//生成KEY
/**
* Retrieves a value from cache with a specified key.
* @param mixed $key a key identifying the cached value. This can be a simple string or
* a complex data structure consisting of factors representing the key.
* @return mixed the value stored in cache, false if the value is not in the cache, expired,
* or the dependency associated with the cached data has changed.
*/
public function get($key);//按Key获取数据
/**
* Checks whether a specified key exists in the cache.
* This can be faster than getting the value from the cache if the data is big.
* In case a cache does not support this feature natively, this method will try to simulate it
* but has no performance improvement over getting it.
* Note that this method does not check whether the dependency associated
* with the cached data, if there is any, has changed. So a call to [[get]]
* may return false while exists returns true.
* @param mixed $key a key identifying the cached value. This can be a simple string or
* a complex data structure consisting of factors representing the key.
* @return bool true if a value exists in cache, false if the value is not in the cache or expired.
*/
public function exists($key);//判断相应的Key是否存在
/**
* Retrieves multiple values from cache with the specified keys.
* Some caches (such as memcache, apc) allow retrieving multiple cached values at the same time,
* which may improve the performance. In case a cache does not support this feature natively,
* this method will try to simulate it.
* @param string[] $keys list of string keys identifying the cached values
* @return array list of cached values corresponding to the specified keys. The array
* is returned in terms of (key, value) pairs.
* If a value is not cached or expired, the corresponding array value will be false.
*/
public function multiGet($keys);//获取多个Key的数据
/**
* 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, respectively.
*
* @param mixed $key a key identifying the value to be cached. This can be a simple string or
* a complex data structure consisting of factors representing the key.
* @param mixed $value the value to be cached
* @param int $duration default duration in seconds before the cache will expire. If not set,
* default [[defaultDuration]] value is used.
* @param Dependency $dependency dependency of the cached item. If the dependency changes,
* the corresponding value in the cache will be invalidated when it is fetched via [[get()]].
* This parameter is ignored if [[serializer]] is false.
* @return bool whether the value is successfully stored into cache
*/
public function set($key, $value, $duration = null, $dependency = null);//设置Key对应的数据
/**
* Stores multiple items in cache. Each item contains a value identified by a key.
* If the cache already contains such a key, the existing value and
* expiration time will be replaced with the new ones, respectively.
*
* @param array $items the items to be cached, as key-value pairs.
* @param int $duration default number of seconds in which the cached values will expire. 0 means never expire.
* @param Dependency $dependency dependency of the cached items. If the dependency changes,
* the corresponding values in the cache will be invalidated when it is fetched via [[get()]].
* This parameter is ignored if [[serializer]] is false.
* @return array array of failed keys
*/
public function multiSet($items, $duration = 0, $dependency = null);//多个设置
/**
* 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.
* @param mixed $key a key identifying the value to be cached. This can be a simple string or
* a complex data structure consisting of factors representing the key.
* @param mixed $value the value to be cached
* @param int $duration the number of seconds in which the cached value will expire. 0 means never expire.
* @param Dependency $dependency dependency of the cached item. If the dependency changes,
* the corresponding value in the cache will be invalidated when it is fetched via [[get()]].
* This parameter is ignored if [[serializer]] is false.
* @return bool whether the value is successfully stored into cache
*/
public function add($key, $value, $duration = 0, $dependency = null);
/**
* Stores multiple items in cache. Each item contains a value identified by a key.
* If the cache already contains such a key, the existing value and expiration time will be preserved.
*
* @param array $items the items to be cached, as key-value pairs.
* @param int $duration default number of seconds in which the cached values will expire. 0 means never expire.
* @param Dependency $dependency dependency of the cached items. If the dependency changes,
* the corresponding values in the cache will be invalidated when it is fetched via [[get()]].
* This parameter is ignored if [[serializer]] is false.
* @return array array of failed keys
*/
public function multiAdd($items, $duration = 0, $dependency = null);
/**
* Deletes a value with the specified key from cache.
* @param mixed $key a key identifying the value to be deleted from cache. This can be a simple string or
* a complex data structure consisting of factors representing the key.
* @return bool if no error happens during deletion
*/
public function delete($key);
/**
* Deletes all values from cache.
* Be careful of performing this operation if the cache is shared among multiple applications.
* @return bool whether the flush operation was successful.
*/
public function flush();
/**
* Method combines both [[set()]] and [[get()]] methods to retrieve value identified by a $key,
* or to store the result of $callable execution if there is no cache available for the $key.
*
* Usage example:
*
* ```php
* public function getTopProducts($count = 10) {
* $cache = $this->cache; // Could be Yii::$app->cache
* return $cache->getOrSet(['top-n-products', 'n' => $count], function ($cache) use ($count) {
* return Products::find()->mostPopular()->limit($count)->all();
* }, 1000);
* }
* ```
*
* @param mixed $key a key identifying the value to be cached. This can be a simple string or
* a complex data structure consisting of factors representing the key.
* @param callable|\Closure $callable the callable or closure that will be used to generate a value to be cached.
* In case $callable returns `false`, the value will not be cached.
* @param int $duration default duration in seconds before the cache will expire. If not set,
* [[defaultDuration]] value will be used.
* @param Dependency $dependency dependency of the cached item. If the dependency changes,
* the corresponding value in the cache will be invalidated when it is fetched via [[get()]].
* This parameter is ignored if [[serializer]] is `false`.
* @return mixed result of $callable execution
*/
public function getOrSet($key, $callable, $duration = null, $dependency = null);
}