개념적인 예시
이 예시는 프로토타입 디자인 패턴의 구조를 보여주고 다음 질문에 중점을 둡니다:
패턴은 어떤 클래스들로 구성되어 있나요?
이 클래스들은 어떤 역할을 하나요?
패턴의 요소들은 어떻게 서로 연관되어 있나요?
이 패턴의 구조를 배우면 실제 PHP 사용 사례를 기반으로 하는 다음 예시를 더욱 쉽게 이해할 수 있을 것입니다.
index.php: 개념적인 예시
<?php
namespace RefactoringGuru\Prototype\Conceptual;
/**
* The example class that has cloning ability. We'll see how the values of field
* with different types will be cloned.
*/
class Prototype
{
public $primitive;
public $component;
public $circularReference;
/**
* PHP has built-in cloning support. You can `clone` an object without
* defining any special methods as long as it has fields of primitive types.
* Fields containing objects retain their references in a cloned object.
* Therefore, in some cases, you might want to clone those referenced
* objects as well. You can do this in a special `__clone()` method.
*/
public function __clone()
{
$this->component = clone $this->component;
// Cloning an object that has a nested object with backreference
// requires special treatment. After the cloning is completed, the
// nested object should point to the cloned object, instead of the
// original object.
$this->circularReference = clone $this->circularReference;
$this->circularReference->prototype = $this;
}
}
class ComponentWithBackReference
{
public $prototype;
/**
* Note that the constructor won't be executed during cloning. If you have
* complex logic inside the constructor, you may need to execute it in the
* `__clone` method as well.
*/
public function __construct(Prototype $prototype)
{
$this->prototype = $prototype;
}
}
/**
* The client code.
*/
function clientCode()
{
$p1 = new Prototype();
$p1->primitive = 245;
$p1->component = new \DateTime();
$p1->circularReference = new ComponentWithBackReference($p1);
$p2 = clone $p1;
if ($p1->primitive === $p2->primitive) {
echo "Primitive field values have been carried over to a clone. Yay!\n";
} else {
echo "Primitive field values have not been copied. Booo!\n";
}
if ($p1->component === $p2->component) {
echo "Simple component has not been cloned. Booo!\n";
} else {
echo "Simple component has been cloned. Yay!\n";
}
if ($p1->circularReference === $p2->circularReference) {
echo "Component with back reference has not been cloned. Booo!\n";
} else {
echo "Component with back reference has been cloned. Yay!\n";
}
if ($p1->circularReference->prototype === $p2->circularReference->prototype) {
echo "Component with back reference is linked to original object. Booo!\n";
} else {
echo "Component with back reference is linked to the clone. Yay!\n";
}
}
clientCode();
Output.txt: 실행 결과
Primitive field values have been carried over to a clone. Yay!
Simple component has been cloned. Yay!
Component with back reference has been cloned. Yay!
Component with back reference is linked to the clone. Yay!
실제 사례 예시
프로토타입 패턴은 기존 객체들의 모든 필드를 직접 복사하여 그들을 재구성하는 대신 해당 객체들을 복제하는 편리한 방법을 제공합니다. 직접 접근 방식은 복제되는 객체들의 클래스에 새로운 객체들을 결합할 뿐만 아니라 비공개 필드의 내용을 복사하는 것도 허용하지 않습니다. 프로토타입 패턴은 복제를 복사되는 객체의 클래스 내에서 수행할 수 있도록 합니다. 그렇게 하면 복사되는 클래스의 비공개 필드들에 대한 접근이 제한되지 않습니다.
이 예시는 프로토타입 패턴을 이용해 복잡한 웹페이지 객체를 복제하는 방법을 보여줍니다. 웹페이지는 여러 비공개 필드들이 있으나, 프로토타입 패턴 덕분에 최종 복제 객체에 이러한 필드들이 전달될 것입니다.
index.php: 실제 사례 예시
<?php
namespace RefactoringGuru\Prototype\RealWorld;
/**
* Prototype.
*/
class Page
{
private $title;
private $body;
/**
* @var Author
*/
private $author;
private $comments = [];
/**
* @var \DateTime
*/
private $date;
// +100 private fields.
public function __construct(string $title, string $body, Author $author)
{
$this->title = $title;
$this->body = $body;
$this->author = $author;
$this->author->addToPage($this);
$this->date = new \DateTime();
}
public function addComment(string $comment): void
{
$this->comments[] = $comment;
}
/**
* You can control what data you want to carry over to the cloned object.
*
* For instance, when a page is cloned:
* - It gets a new "Copy of ..." title.
* - The author of the page remains the same. Therefore we leave the
* reference to the existing object while adding the cloned page to the list
* of the author's pages.
* - We don't carry over the comments from the old page.
* - We also attach a new date object to the page.
*/
public function __clone()
{
$this->title = "Copy of " . $this->title;
$this->author->addToPage($this);
$this->comments = [];
$this->date = new \DateTime();
}
}
class Author
{
private $name;
/**
* @var Page[]
*/
private $pages = [];
public function __construct(string $name)
{
$this->name = $name;
}
public function addToPage(Page $page): void
{
$this->pages[] = $page;
}
}
/**
* The client code.
*/
function clientCode()
{
$author = new Author("John Smith");
$page = new Page("Tip of the day", "Keep calm and carry on.", $author);
// ...
$page->addComment("Nice tip, thanks!");
// ...
$draft = clone $page;
echo "Dump of the clone. Note that the author is now referencing two objects.\n\n";
print_r($draft);
}
clientCode();
Output.txt: 실행 결과
Dump of the clone. Note that the author is now referencing two objects.
RefactoringGuru\Prototype\RealWorld\Page Object
(
[title:RefactoringGuru\Prototype\RealWorld\Page:private] => Copy of Tip of the day
[body:RefactoringGuru\Prototype\RealWorld\Page:private] => Keep calm and carry on.
[author:RefactoringGuru\Prototype\RealWorld\Page:private] => RefactoringGuru\Prototype\RealWorld\Author Object
(
[name:RefactoringGuru\Prototype\RealWorld\Author:private] => John Smith
[pages:RefactoringGuru\Prototype\RealWorld\Author:private] => Array
(
[0] => RefactoringGuru\Prototype\RealWorld\Page Object
(
[title:RefactoringGuru\Prototype\RealWorld\Page:private] => Tip of the day
[body:RefactoringGuru\Prototype\RealWorld\Page:private] => Keep calm and carry on.
[author:RefactoringGuru\Prototype\RealWorld\Page:private] => RefactoringGuru\Prototype\RealWorld\Author Object
*RECURSION*
[comments:RefactoringGuru\Prototype\RealWorld\Page:private] => Array
(
[0] => Nice tip, thanks!
)
[date:RefactoringGuru\Prototype\RealWorld\Page:private] => DateTime Object
(
[date] => 2018-06-04 14:50:39.306237
[timezone_type] => 3
[timezone] => UTC
)
)
[1] => RefactoringGuru\Prototype\RealWorld\Page Object
*RECURSION*
)
)
[comments:RefactoringGuru\Prototype\RealWorld\Page:private] => Array
(
)
[date:RefactoringGuru\Prototype\RealWorld\Page:private] => DateTime Object
(
[date] => 2018-06-04 14:50:39.306272
[timezone_type] => 3
[timezone] => UTC
)
)