PHP 之 SplObjectStorage对象存储

摘要：类实现了对象存储映射表，应用于需要唯一标识多个对象的存储场景。在之前仅能存储对象，之后可以针对每个对象添加一条对应的数据。实际上他们并没有直接的关系。

php.net上的定义 The SplObjectStorage class provides a map from objects to data or, by ignoring data, an object set. This dual purpose can be useful in many cases involving the need to uniquely identify objects. 翻译:SplObjectStorage类提供从对象到数据映射功能，或者，通过忽视数据来提供对象集合，在很多涉及需要唯一对象的许多情况下，这两点是十分有用的。

SplObjectStorage类实现了对象存储映射表，应用于需要唯一标识多个对象的存储场景。 在PHP5.3.0之前仅能存储对象，之后可以针对每个对象添加一条对应的数据。 SplObjectStorage类的数据存储依赖于PHP的HashTable实现，与传统的使用数组和spl_object_hash函数生成数组key相比， 其直接使用HashTable的实现在性能上有较大的优势。 有一些奇怪的是，在PHP手册中，SplObjectStorage类放在数据结构目录下。 但是他的实现和观察者模式的接口放在同一个文件（ext/spl/spl_observer.c）。 实际上他们并没有直接的关系。《深入理解php内核》

class SplObjectStorage implements Countable, Iterator, Serializable, ArrayAccess {
 //省略，下边详细解释以及翻译
}

此类实现了 Countable, Iterator, Serializable, ArrayAccess 四个接口，分别对应统计，迭代，序列化和数组访问，四个接口分别说明如下

2.1 Countable

此接口中只有一方法count()，看SplObjectStorage 类中此方法的说明（源码位置在php.jar/stubs/SPL/SPL_c1.php文件的1979行，可以用phpstorm按住command鼠标左键跳转过去）

/**
 * Returns the number of objects in the storage //返回存储中的对象数量
 * @link https://php.net/manual/en/splobjectstorage.count.php
 * @return int The number of objects in the storage.
 * @since 5.1.0
 */
public function count () {}

翻译注释:Returns the number of objects in the storage //返回存储中的对象数量

2.2 Iterator

接口注释Interface for external iterators or objects that can be iterated 的翻译为外部迭代器或可以迭代的对象的接口，此接口中有5个方法分别如下(对应注释中有翻译)

/**
 * Rewind the iterator to the first storage element //将迭代器回到第一个存储的元素
 * @link https://php.net/manual/en/splobjectstorage.rewind.php
 * @return void 
 * @since 5.1.0
 */
public function rewind () {}

/**
 * Returns if the current iterator entry is valid //返回当前迭代器条目是否有效
 * @link https://php.net/manual/en/splobjectstorage.valid.php
 * @return bool true if the iterator entry is valid, false otherwise.
 * @since 5.1.0
 */
public function valid () {}

/**
 * Returns the index at which the iterator currently is//返回当前迭代对应的索引
 * @link https://php.net/manual/en/splobjectstorage.key.php
 * @return int The index corresponding to the position of the iterator.
 * @since 5.1.0
 */
public function key () {}

/**
 * Returns the current storage entry //返回当前存储的条目
 * @link https://php.net/manual/en/splobjectstorage.current.php
 * @return object The object at the current iterator position.
 * @since 5.1.0
 */
public function current () {}

/**
 * Move to the next entry //移到下一个条目
 * @link https://php.net/manual/en/splobjectstorage.next.php
 * @return void 
 * @since 5.1.0
 */
public function next () {}

2.3 Serializable

接口注释Interface for customized serializing.的翻译为用于自定义序列化的接口，此接口中有2个方法分别如下(对应注释中有翻译)

/**
 * Serializes the storage //序列化存储
 * @link https://php.net/manual/en/splobjectstorage.serialize.php
 * @return string A string representing the storage. //返回表示存储的字符串
 * @since 5.2.2
 */
public function serialize () {}
/**
 * Unserializes a storage from its string representation //从一个字符串表示中对存储反序列化
 * @link https://php.net/manual/en/splobjectstorage.unserialize.php
 * @param string $serialized 

 * The serialized representation of a storage.
 * 
 * @return void 
 * @since 5.2.2
 */
public function unserialize ($serialized) {}

2.4 ArrayAccess

接口注释Interface to provide accessing objects as arrays.的翻译为提供像访问数组一样访问对象的接口，此接口中有4个方法分别如下(对应注释中有翻译)

/**
 * Checks whether an object exists in the storage //检查存储中是否存在找个对象
 * @link https://php.net/manual/en/splobjectstorage.offsetexists.php
 * @param object $object 

 * The object to look for.
 * 
 * @return bool true if the object exists in the storage,
 * and false otherwise.
 * @since 5.3.0
 */
public function offsetExists ($object) {}

/**
 * Associates data to an object in the storage //给存储中的对象赋值
 * @link https://php.net/manual/en/splobjectstorage.offsetset.php
 * @param object $object 

 * The object to associate data with.
 * 
 * @param mixed $data [optional] 

 * The data to associate with the object.
 * 
 * @return void 
 * @since 5.3.0
 */
public function offsetSet ($object, $data = null) {}

/**
 * Removes an object from the storage //从存储中删除一个对象
 * @link https://php.net/manual/en/splobjectstorage.offsetunset.php
 * @param object $object 

 * The object to remove.
 * 
 * @return void 
 * @since 5.3.0
 */
public function offsetUnset ($object) {}

/**
 * Returns the data associated with an object //从存储中获得一个对象
 * @link https://php.net/manual/en/splobjectstorage.offsetget.php
 * @param object $object 

 * The object to look for.
 * 
 * @return mixed The data previously associated with the object in the storage.
 * @since 5.3.0
 */
public function offsetGet ($object) {}

此接口的功能用代码简单说明如下

$collection = new SuporCollection();//假设有一Collection类，并且已经实现了ArrayAccess 接口
$collection["a"] = 10;//我们可以像给数组赋值一样给此对象赋值
var_dump($collection["a"]);//也可以使用取数组值的方法取得对象的属性 而不用 "->"
//输出 int(10)

在每个方法的注释中有对应翻译，来说明这个方法的作用

/**
 * Adds an object in the storage //向存储中添加一个对象
 * @link https://php.net/manual/en/splobjectstorage.attach.php
 * @param object $object 

 * The object to add.
 * 
 * @param mixed $data [optional] 

 * The data to associate with the object.
 * 
 * @return void 
 * @since 5.1.0
 */
public function attach ($object, $data = null) {}

/**
 * Removes an object from the storage //从存储中删除一个对象
 * @link https://php.net/manual/en/splobjectstorage.detach.php
 * @param object $object 

 * The object to remove.
 * 
 * @return void 
 * @since 5.1.0
 */
public function detach ($object) {}

/**
 * Checks if the storage contains a specific object //检查存储中是否包含特定的对象
 * @link https://php.net/manual/en/splobjectstorage.contains.php
 * @param object $object 

 * The object to look for.
 * 
 * @return bool true if the object is in the storage, false otherwise.
 * @since 5.1.0
 */
public function contains ($object) {}

/**
 * Adds all objects from another storage //添加一个存储中所有对象
 * @link https://php.net/manual/en/splobjectstorage.addall.php
 * @param SplObjectStorage $storage 

 * The storage you want to import.
 * 
 * @return void 
 * @since 5.3.0
 */
public function addAll ($storage) {}

/**
 * Removes objects contained in another storage from the current storage //从当前存储中删除另一个存储中包含的对象
 * @link https://php.net/manual/en/splobjectstorage.removeall.php
 * @param SplObjectStorage $storage 

 * The storage containing the elements to remove.
 * 
 * @return void 
 * @since 5.3.0
 */
public function removeAll ($storage) {}

/**
 *从当前存储中删除另一个存储中不包含的对象
 * Removes all objects except for those contained in another storage from the current storage 
 * @link https://php.net/manual/en/splobjectstorage.removeallexcept.php
 * @param SplObjectStorage $storage 

 * The storage containing the elements to retain in the current storage.
 * 
 * @return void
 * @since 5.3.6
 */
public function removeAllExcept ($storage) {}

/**
 * Returns the data associated with the current iterator entry //返回当前迭代器条目相关的数据
 * @link https://php.net/manual/en/splobjectstorage.getinfo.php
 * @return mixed The data associated with the current iterator position.
 * @since 5.3.0
 */
public function getInfo () {}

/**
 * Sets the data associated with the current iterator entry//设置当前迭代器条目相关的数据
 * @link https://php.net/manual/en/splobjectstorage.setinfo.php
 * @param mixed $data 

 * The data to associate with the current iterator entry.
 * 
 * @return void 
 * @since 5.3.0
 */
public function setInfo ($data) {}
/**
 * Calculate a unique identifier for the contained objects //给包含的对象计算一个唯一ID
 * @link https://php.net/manual/en/splobjectstorage.gethash.php
 * @param $object  

 * object whose identifier is to be calculated.
 * @return string A string with the calculated identifier.
 * @since 5.4.0
*/
public function getHash($object) {}
        

SplObjectStorage的对象操作

//假设有三个Collection对象
$collection1 = new SuporCollection(["a" => "aa", "b" => "bb"]);
$collection2 = new SuporCollection(["c" => "cc", "d" => "dd"]);
$collection3 = new SuporCollection(["e" => "ee", "f" => "ff"]);

$splStorage = new SplObjectStorage();
$splStorage->attach($collection1);
//传入相同的对象会被替代
$splStorage->attach($collection1);
$splStorage->attach($collection2);
$splStorage->attach($collection3);

//统计$splStorage中有多少个对象
$count = $splStorage->count();
var_dump($count);
//得到某一对象的哈希值
$hash1 = $splStorage->getHash($collection1);
var_dump($hash1);

//检查存储中是否包含$collection3
$contains3 = $splStorage->contains($collection3);
var_dump($contains3);

//将指针后移
$splStorage->next();
//读取移动后的key
$key = $splStorage->key();
var_dump($key);

//删除某个对象
$splStorage->detach($collection3);
//统计删除后的数量
$count = $splStorage->count();
var_dump($count);

//遍历$splStorage所有对象
//遍历前先重置一下指针
$splStorage->rewind();
//当当前迭代器条目返回真时
while ($splStorage->valid()) {
    //打印当前条目
    var_dump($splStorage->current());
    //指针后移
    $splStorage->next();
}

代码执行结果如下: