文章来源refactoringguru.cn/design-patt…
PHP 原型模式讲解和代码示例
原型是一种创建型设计模式， 使你能够复制对象， 甚至是复杂对象， 而又无需使代码依赖它们所属的类。
所有的原型类都必须有一个通用的接口， 使得即使在对象所属的具体类未知的情况下也能复制对象。 原型对象可以生成自身的完整副本， 因为相同类的对象可以相互访问对方的私有成员变量。
复杂度：******
流行度：******
使用示例： PHP 中提供立即可用的原型模式。 你可以使用 clone关键字创建一个对象的完整副本。 如果想要某个类支持克隆功能， 你需要实现 __clone方法。
识别方法： 原型可以简单地通过 clone或 copy等方法来识别。
真实世界示例
原型模式提供了一种复制已有对象的简便方式， 可代替直接复制对象的所有成员变量来对对象进行重构的方法。 直接复制的方式不仅让你与被克隆类所属的对象相耦合， 还不允许你复制私有成员变量的内容。 原型模式让你能够在被克隆类的内部进行克隆工作， 因此可以不受限制地访问类的私有成员变量。
本例说明了如何使用原型模式克隆复杂的页面对象。 页面类拥有许多私有成员变量， 但它们都通过原型模式被复制到了克隆对象中。
** index.php: 真实世界示例
<?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: 执行结果
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
)
)
