php组合模式应用场景 PHP 组合模式

目的

以单个对象的方式来对待一组对象

例子

• form类的实例包含多个子元素，而它也像单个子元素那样响应render()请求，当调用 render() 方法时，它会历遍所有的子元素，调用 render() 方法

UML 图

代码

Renderable.php

<?php

declare(strict_types=1);

namespace DesignPatternsStructuralComposite;

interface Renderable
{
    public function render(): string;
}

Form.php

<?php

declare(strict_types=1);

namespace DesignPatternsStructuralComposite;


class Form implements Renderable
{
    
    private array $elements;

    
    public function render(): string
    {
        $formCode = "<form>";

        foreach ($this->elements as $element) {
            $formCode .= $element->render();
        }

        return $formCode . "</form>";
    }

    public function addElement(Renderable $element)
    {
        $this->elements[] = $element;
    }
}

InputElement.php

<?php

declare(strict_types=1);

namespace DesignPatternsStructuralComposite;

class InputElement implements Renderable
{
    public function render(): string
    {
        return "<input type="text" />";
    }
}

TextElement.php

<?php

declare(strict_types=1);

namespace DesignPatternsStructuralComposite;

class TextElement implements Renderable
{
    public function __construct(private string $text)
    {
    }

    public function render(): string
    {
        return $this->text;
    }
}

测试

Tests/CompositeTest.php

<?php

declare(strict_types=1);

namespace DesignPatternsStructuralCompositeTests;

use DesignPatternsStructuralCompositeForm;
use DesignPatternsStructuralCompositeTextElement;
use DesignPatternsStructuralCompositeInputElement;
use PHPUnitFrameworkTestCase;

class CompositeTest extends TestCase
{
    public function testRender()
    {
        $form = new Form();
        $form->addElement(new TextElement("Email:"));
        $form->addElement(new InputElement());
        $embed = new Form();
        $embed->addElement(new TextElement("Password:"));
        $embed->addElement(new InputElement());
        $form->addElement($embed);

        // This is just an example, in a real world scenario it is important to remember that web browsers do not
        // currently support nested forms

        $this->assertSame(
            "<form>Email:<input type="text" /><form>Password:<input type="text" /></form></form>",
            $form->render()
        );
    }
}