设计模式之原型模式的原理和实现方法
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原型模式是一种创建型设计模式,使你能够复制已有对象,而又无需使代码依赖它们所属的类。
代码示例
<?php
/**
* Prototype Design Pattern
*
* Intent: Lets you copy existing objects without making your code dependent on
* their classes.
*
* Example: The Prototype pattern provides a convenient way to replicate
* existing objects instead of reconstructing them and copying over all of their
* fields directly. The direct approach not only couples you to the classes of
* the objects being cloned, but also doesn't allow you to copy the contents of
* the private fields. The Prototype pattern lets you perform the cloning within
* the context of the cloned class, where the access to the class' private
* fields is not restricted.
*
* This example shows you how to clone a complex Page object using the Prototype
* pattern. The Page class has lots of private fields, which will be carried
* over to the cloned object thanks to the Prototype pattern.
*/
/**
* 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();
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如未按上述操作复制或转载,本站有权追究法律责任。
若本站内容侵犯了原著者的合法权益,可联系我们进行处理。