有很多关于PHP中工厂方法实现的文章。我想在PHP中为我的MongoDB实现实现实现这样一个方法。
我写的代码如下。请看那个代码。
<?php
class Document {
public $value = array();
function __construct($doc = array()) {
$this->value = $doc;
}
/** User defined functions here **/
}
class Collection extends Document {
//initialize database
function __construct() {
global $mongo;
$this->db = Collection::$DB_NAME;
}
//select collection in database
public function changeCollection($name) {
$this->collection = $this->db->selectCollection($name);
}
//user defined method
public function findOne($query = array(), $projection = array()) {
$doc = $this->collection->findOne($query, $projection);
return isset($doc) ? new Document($doc) : false;
}
public function find($query = array(), $projection = array()) {
$result = array();
$cur = $this->collection->find($query, $projection);
foreach($cur as $doc) {
array_push($result, new Document($doc));
}
return $result;
}
/* Other user defined methods will go here */
}
/* Factory class for collection */
class CollectionFactory {
private static $engine;
private function __construct($name) {}
private function __destruct() {}
private function __clone() {}
public static function invokeMethod($collection, $name, $params) {
static $initialized = false;
if (!$initialized) {
self::$engine = new Collection($collection);
$initialized = true;
}
self::$engine->changeCollection($collection);
return call_user_func_array(array(self::$engine, $name), $params);
}
}
/* books collection */
class Books extends CollectionFactory {
public static function __callStatic($name, $params) {
return parent::invokeMethod('books', $name, $params);
}
}
/* authors collection */
class Authors extends CollectionFactory {
public static function __callStatic($name, $params) {
return parent::invokeMethod('authors', $name, $params);
}
}
/* How to use */
$books = Books::findOne(array('name' => 'Google'));
$authors = Authors::findOne(array('name' => 'John'));
Authors::update(array('name' => 'John'), array('name' => 'John White'));
Authors::remove(array('name' => 'John'));
?>
我的问题是:-
- 这是工厂方法的正确PHP实现吗
- 这种实施是否存在任何问题
- 对于这种情况,有没有更好的方法
谢谢大家的回答。
- 嗯,不,因为通过您的代码段,您可以使集合类上的所有方法都可用于静态调用。这不是(抽象的)工厂模式的目的
- 像
__callStatic
或call_user_func_array
这样的(魔术)方法非常棘手,因为开发人员可以使用它来调用每个方法 - 你真正想做什么?实现工厂模式或者使用静态的一行方法来实现MongoDB
如果图书和作者集合的实现有不同的方法(比如getName()等),我建议这样做:
class BookCollection extends Collection {
protected $collection = 'book';
public function getName() {
return 'Book!';
}
}
class AuthorCollection extends Collection {
protected $collection = 'author';
public function getName() {
return 'Author!';
}
}
class Collection {
private $adapter = null;
public function __construct() {
$this->getAdapter()->selectCollection($this->collection);
}
public function findOne($query = array(), $projection = array()) {
$doc = $this->getAdapter()->findOne($query, $projection);
return isset($doc) ? new Document($doc) : false;
}
public function getAdapter() {
// some get/set dep.injection for mongo
if(isset($this->adapter)) {
return $this->adapter;
}
return new Mongo();
}
}
class CollectionFactory {
public static function build($collection)
{
switch($collection) {
case 'book':
return new BookCollection();
break;
case 'author':
return new AuthorCollection();
break;
}
// or use reflection magic
}
}
$bookCollection = CollectionFactory::build('book');
$bookCollection->findOne(array('name' => 'Google'));
print $bookCollection->getName(); // Book!
编辑:静态单行方法的示例
class BookCollection extends Collection {
protected static $name = 'book';
}
class AuthorCollection extends Collection {
protected static $name = 'author';
}
class Collection {
private static $adapter;
public static function setAdapter($adapter) {
self::$adapter = $adapter;
}
public static function getCollectionName() {
$self = new static();
return $self::$name;
}
public function findOne($query = array(), $projection = array()) {
self::$adapter->selectCollection(self::getCollectionName());
$doc = self::$adapter->findOne($query, $projection);
return $doc;
}
}
Collection::setAdapter(new Mongo()); //initiate mongo adapter (once)
BookCollection::findOne(array('name' => 'Google'));
AuthorCollection::findOne(array('name' => 'John'));
Collection
扩展Document
有意义吗?在我看来,Collection
可能有Document
,但不是Document
。。。所以我想说这个代码看起来有点混乱。
此外,对于factory方法,您确实希望使用它来实例化Document
或Collection
的不同具体子类。假设您只使用过一种类型的Collection
,以便于交谈;那么您的工厂类只需要关注不同的CCD_ 11子类。
因此,您可能有一个Document
类,它需要一个表示单个文档的原始array
。
class Document
{
private $_aRawDoc;
public function __construct(array $aRawDoc)
{
$this->_aRawDoc = $aRawDoc;
}
// Common Document methods here..
}
然后指定文档类型的专用子类
class Book extends Document
{
// Specialized Book functions ...
}
对于工厂类,您需要一些东西,然后在从光标上读取原始结果时将其包装起来。PDO让我们开箱即用(例如,请参阅PDOStatement::fetchObject
的$className
参数),但我们需要使用装饰器,因为PHP不允许我们对Mongo扩展有那么多兴趣。
class MongoCursorDecorator implements MongoCursorInterface, Iterator
{
private $_sDocClass; // Document class to be used
private $_oCursor; // Underlying MongoCursor instance
private $_aDataObjects = []; // Concrete Document instances
// Decorate the MongoCursor, so we can wrap the results
public function __construct(MongoCursor $oCursor, $sDocClass)
{
$this->_oCursor = $oCursor;
$this->_sDocClass = $sDocClass;
}
// Delegate to most of the stock MongoCursor methods
public function __call($sMethod, array $aParams)
{
return call_user_func_array([$this->_oCursor, $sMethod], $aParams);
}
// Wrap the raw results by our Document classes
public function current()
{
$key = $this->key();
if(!isset($this->_aDataObjects[$key]))
$this->_aDataObjects[$key] =
new $this->sDocClass(parent::current());
return $this->_aDataObjects[$key];
}
}
现在是一个如何查询mongo以查找给定作者的书籍的示例
$m = new MongoClient();
$db = $m->selectDB('test');
$collection = new MongoCollection($db, 'book');
// search for author
$bookQuery = array('Author' => 'JR Tolken');
$cursor = $collection->find($bookQuery);
// Wrap the native cursor by our Decorator
$cursor = new MongoCursorDecorator($cursor, 'Book');
foreach ($cursor as $doc) {
var_dump($doc); // This will now be an instance of Book
}
你可以用MongoCollection
子类把它收紧一点,无论如何你也可以拥有它,因为你也希望findOne
方法修饰那些原始结果。
class MongoDocCollection extends MongoCollection
{
public function find(array $query=[], array $fields=[])
{
// The Document class name is based on the collection name
$sDocClass = ucfirst($this->getName());
$cursor = parent::find($query, $fields);
$cursor = new MongoCursorDecorator($cursor, $sDocClass);
return $cursor;
}
public function findOne(
array $query=[], array $fields=[], array $options=[]
) {
$sDocClass = ucfirst($this->getName());
return new $sDocClass(parent::findOne($query, $fields, $options));
}
}
然后我们的样品使用变成
$m = new MongoClient();
$db = $m->selectDB('test');
$collection = new MongoDocCollection($db, 'book');
// search for author
$bookQuery = array('Author' => 'JR Tolken');
$cursor = $collection->find($bookQuery);
foreach($cursor as $doc) {
var_dump($doc); // This will now be an instance of Book
}