purpose
A group of objects is handled in the same way as a single instance of that object.
Example
-
An instance of the form class contains multiple child elements, and it responds to the render() request like a single child element. When the render() method is called, it will traverse all the child elements and call the render() method
-
Zend_Config: A configuration option tree, each option itself is a Zend_Config object
UML graphics
Code
- RenderableInterface.php
<?php
namespace DesignPatterns\Structural\Composite;
interface RenderableInterface
{
public function render(): string;
}
- Form.php
<?php
namespace DesignPatterns\Structural\Composite;
/**
* 该组合内的节点必须派生于该组件契约。为了构建成一个组件树，
* 此为强制性操作。
*/
class Form implements RenderableInterface
{
/**
* @var RenderableInterface[]
*/
private $elements;
/**
* 遍历所有元素，并对他们调用 render() 方法，然后返回表单的完整
* 的解析表达。
*
* 从外部上看，我们不会看到遍历过程，该表单的操作过程与单一对
* 象实例一样
*
* @return string
*/
public function render(): string
{
$formCode = '<form>';
foreach ($this->elements as $element) {
$formCode .= $element->render();
}
$formCode .= '</form>';
return $formCode;
}
/**
* @param RenderableInterface $element
*/
public function addElement(RenderableInterface $element)
{
$this->elements[] = $element;
}
}
- InputElement.php
<?php
namespace DesignPatterns\Structural\Composite;
class InputElement implements RenderableInterface
{
public function render(): string
{
return '<input type="text" />';
}
}
- TextElement.php
<?php
namespace DesignPatterns\Structural\Composite;
class TextElement implements RenderableInterface
{
/**
* @var string
*/
private $text;
public function __construct(string $text)
{
$this->text = $text;
}
public function render(): string
{
return $this->text;
}
}
test
- Tests/CompositeTest.php
<?php
namespace DesignPatterns\Structural\Composite\Tests;
use DesignPatterns\Structural\Composite;
use PHPUnit\Framework\TestCase;
class CompositeTest extends TestCase
{
public function testRender()
{
$form = new Composite\Form();
$form->addElement(new Composite\TextElement('Email:'));
$form->addElement(new Composite\InputElement());
$embed = new Composite\Form();
$embed->addElement(new Composite\TextElement('Password:'));
$embed->addElement(new Composite\InputElement());
$form->addElement($embed);
// 此代码仅作示例。在实际场景中，现在的网页浏览器根本不支持
// 多表单嵌套，牢记该点非常重要
$this->assertEquals(
'<form>Email:<input type="text" /><form>Password:<input type="text" /></form></form>',
$form->render()
);
}
}
The Growth Path of PHP Internet Architect * The Ultimate Guide to "Design Patterns"
PHP Internet Architect 50K Growth Guide + Industry Problem Solving Guide (Continuous Update)
Interview with 10 companies, get 9 offers, PHP interview questions in 2020
★If you like my article and want to communicate and learn with more senior developers, get more technical consultation and guidance related to interviews with big companies, welcome to join our group, password: phpzh (group number 856460874).
The latest PHP advanced tutorial in 2020, full series!
If the content is good, I hope everyone will support and encourage you to give a like/like, and welcome to communicate together; in addition, if you have any questions, you can suggest what you want to see in the comments.