Decorator

Purpose:

To dynamically add new functionality to class instance.

Booking.php

<?php

namespace DesignPatterns\Structural\Decorator;

interface Booking
{
    public function calculatePrice(): int;

    public function getDescription(): string;
}

　　

BookingDecorator.php

<?php

namespace DesignPatterns\Structural\Decorator;

abstract class BookingDecorator implements Booking
{
    /**
     * @var Booking
     */
    protected $booking;

    public function __construct(Booking $booking)
    {
        $this->booking = $booking;
    }
}

　　

DoubleRoomBooking.php

<?php

namespace DesignPatterns\Structural\Decorator;

class DoubleRoomBooking implements Booking
{
    public function calculatePrice(): int
    {
        return 40;
    }

    public function getDescription(): string
    {
        return 'double room';
    }
}

　　

ExtraBed.php

<?php

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

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';
    }
}

　　

Tests/DecoratorTest.php

<?php

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->assertEquals(40, $booking->calculatePrice());
        $this->assertEquals('double room', $booking->getDescription());
    }

    public function testCanCalculatePriceForDoubleRoomBookingWithWiFi()
    {
        $booking = new DoubleRoomBooking();
        $booking = new WiFi($booking);

        $this->assertEquals(42, $booking->calculatePrice());
        $this->assertEquals('double room with wifi', $booking->getDescription());
    }

    public function testCanCalculatePriceForDoubleRoomBookingWithWiFiAndExtraBed()
    {
        $booking = new DoubleRoomBooking();
        $booking = new WiFi($booking);
        $booking = new ExtraBed($booking);

        $this->assertEquals(72, $booking->calculatePrice());
        $this->assertEquals('double room with wifi with extra bed', $booking->getDescription());
    }
}