inanzzz | PHP ile Strategy tasarım deseni örneği

Strateji modeli, çalışma zamanında sağlanan bilgilere dayanarak bazı mantıkları yürütmemiz gerektiğinde kullanılır. Teknik olarak if..else, select .. case vs. gibi koşullu ifadelerle aynıdır ama OOP stilinde. SOLID'in Açık/Kapalı Prensibi için harika bir örnektir. Bu modeli kullanmanın birkaç yolu olabilir, ancak ben en yaygın varyasyonlara değineceğim.

Mesaj yayınlama stratejisi

Classlar

class MessagePublisher
{
    private $strategy;

    public function __construct(StrategyInterface $strategy)
    {
        $this->strategy = $strategy;
    }

    public function publish(string $message): string
    {
        return $this->strategy->process($message);
    }
}

interface StrategyInterface
{
    public function process(string $message): string;
}

class FacebookStrategy implements StrategyInterface
{
    public function process(string $message): string
    {
        return sprintf('Message "%s" published on Facebook.', $message);
    }
}

class TwitterStrategy implements StrategyInterface
{
    public function process(string $message): string
    {
        return sprintf('Message "%s" published on Twitter.', $message);
    }
}

Kullanımı

require_once 'MessagePublisher.php';

$messagePublisher = new MessagePublisher(new FacebookStrategy());
echo $messagePublisher->publish('Hello');

echo PHP_EOL;

$messagePublisher = new MessagePublisher(new TwitterStrategy());
echo $messagePublisher->publish('Hello');

echo PHP_EOL;

Sonuç

$ php oop/MessagePublisher/index.php 
Message "Hello" published on Facebook.
Message "Hello" published on Twitter.

Ev boyama stratejisi

Classlar

class HomePainter
{
    private $painters;

    public function __construct(array $painters)
    {
        $this->painters = $painters;
    }

    public function start(Home $home, string $section): ?string
    {
        /** @var StrategyInterface $painter */
        foreach ($this->painters as $painter) {
            if ($painter->canPaint($section)) {
                return $painter->paint($home);
            }
        }

        return null;
    }
}

class Home
{
    public function doors(): string
    {
        return 'Doors painted yellow';
    }

    public function steps(): string
    {
        return 'Steps painted blue';
    }
}

interface StrategyInterface
{
    public function canPaint(string $section): bool;

    public function paint(Home $home): string;
}

class YellowPainterStrategy implements StrategyInterface
{
    public function canPaint(string $section): bool
    {
        return 'doors' === $section;
    }

    public function paint(Home $home): string
    {
        return $home->doors();
    }
}

class BluePainterStrategy implements StrategyInterface
{
    public function canPaint(string $section): bool
    {
        return 'steps' === $section;
    }

    public function paint(Home $home): string
    {
        return $home->steps();
    }
}

Kullanımı

require_once 'HomePainter.php';

$home = new Home();

$homePainter = new HomePainter([
    new YellowPainterStrategy(),
    new BluePainterStrategy(),
]);

echo $homePainter->start($home, 'doors');

echo PHP_EOL;

echo $homePainter->start($home, 'steps');

echo PHP_EOL;

Sonuç

$ php oop/HomePainter/index.php 
Doors painted yellow
Steps painted blue

Numara işleme stratejisi

Classlar

class NumberProcessor
{
    private $strategies;

    public function addProcessor(StrategyInterface $strategy)
    {
        $this->strategies[] = $strategy;

        return $this;
    }

    public function run(int $number): int
    {
        /** @var StrategyInterface $strategy */
        foreach ($this->strategies as $strategy) {
            $number = $strategy->process($number);
        }

        return $number;
    }
}

interface StrategyInterface
{
    public function process(int $number): int;
}

class SumStrategy implements StrategyInterface
{
    public function process(int $number): int
    {
        return $number + $number;
    }
}

class MultiplyStrategy implements StrategyInterface
{
    public function process(int $number): int
    {
        return $number * $number;
    }
}

Kullanımı

require_once 'NumberProcessor.php';

$numberProcessor = new NumberProcessor();
$numberProcessor
    ->addProcessor(new SumStrategy())
    ->addProcessor(new MultiplyStrategy());

echo $numberProcessor->run(4);

echo PHP_EOL;

Sonuç

$ php oop/NumberProcessor/index.php 
64