PHP设计模式 PHP 装饰器模式

目的

动态地为类的实例添加功能

例子

• Web Service层：REST服务的JSON与XML装饰器（当然，在此只能使用其中的一种）

UML 图

代码

Booking.php

<?php
declare(strict_types=1);
namespace DesignPatterns\Structural\Decorator;
interface Booking
{
    public function calculatePrice(): int;
    public function getDescription(): string;
}

BookingDecorator.php

<?php
declare(strict_types=1);
namespace DesignPatterns\Structural\Decorator;
abstract class BookingDecorator implements Booking
{
    public function __construct(protected Booking $booking)
    {
    }
}

DoubleRoomBooking.php

<?php
declare(strict_types=1);
namespace DesignPatterns\Structural\Decorator;
class DoubleRoomBooking implements Booking
{
    public function calculatePrice(): int
    {
        return 40;
    }
    public function getDescription(): string
    {
        return 'double room';
    }
}

ExtraBed.php

<?php
declare(strict_types=1);
namespace DesignPatterns\Structural\Decorator;
class ExtraBed extends BookingDecorator
{
    private const PRICE = 30;
    public function calculatePrice(): int
    {
        return $this->booking->calculatePrice() + self::PRICE;
    }
    public function getDescription(): string
    {
        return $this->booking->getDescription() . ' with extra bed';
    }
}

WiFi.php

<?php
declare(strict_types=1);
namespace DesignPatterns\Structural\Decorator;
class WiFi extends BookingDecorator
{
    private const PRICE = 2;
    public function calculatePrice(): int
    {
        return $this->booking->calculatePrice() + self::PRICE;
    }
    public function getDescription(): string
    {
        return $this->booking->getDescription() . ' with wifi';
    }
}

测试

Tests/DecoratorTest.php

<?php
declare(strict_types=1);
namespace DesignPatterns\Structural\Decorator\Tests;
use DesignPatterns\Structural\Decorator\DoubleRoomBooking;
use DesignPatterns\Structural\Decorator\ExtraBed;
use DesignPatterns\Structural\Decorator\WiFi;
use PHPUnit\Framework\TestCase;
class DecoratorTest extends TestCase
{
    public function testCanCalculatePriceForBasicDoubleRoomBooking()
    {
        $booking = new DoubleRoomBooking();
        $this->assertSame(40, $booking->calculatePrice());
        $this->assertSame('double room', $booking->getDescription());
    }
    public function testCanCalculatePriceForDoubleRoomBookingWithWiFi()
    {
        $booking = new DoubleRoomBooking();
        $booking = new WiFi($booking);
        $this->assertSame(42, $booking->calculatePrice());
        $this->assertSame('double room with wifi', $booking->getDescription());
    }
    public function testCanCalculatePriceForDoubleRoomBookingWithWiFiAndExtraBed()
    {
        $booking = new DoubleRoomBooking();
        $booking = new WiFi($booking);
        $booking = new ExtraBed($booking);
        $this->assertSame(72, $booking->calculatePrice());
        $this->assertSame('double room with wifi with extra bed', $booking->getDescription());
    }
}