2.5. Decorator

2.5.1. Amaç

Sınıf örneklerine (instance) dinamik olarak yeni işlevler eklemek.

2.5.2. Örnekler

  • Web Servisi Katmanı (Layer): Bir REST servisi için kullanılan JSON ve XML bezeyicileri (not: elbette böyle bir durumda bunlardan yalnızca bir tanesine izin verilmiş olabilir).

2.5.3. UML Diyagramı

Alt Decorator UML Diagram

2.5.4. Kod

Bu kodu Github üzerinde de bulabilirsiniz.

Booking.php

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<?php

declare(strict_types=1);

namespace DesignPatterns\Structural\Decorator;

interface Booking
{
    public function calculatePrice(): int;

    public function getDescription(): string;
}

BookingDecorator.php

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<?php

declare(strict_types=1);

namespace DesignPatterns\Structural\Decorator;

abstract class BookingDecorator implements Booking
{
    public function __construct(protected Booking $booking)
    {
    }
}

DoubleRoomBooking.php

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<?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

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<?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

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<?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';
    }
}

2.5.5. Test

Tests/DecoratorTest.php

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<?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());
    }
}