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전략

PHP로 작성된 전략

전략은 행동들의 객체들을 객체들로 변환하며 이들이 원래 콘텍스트 객체 내에서 상호 교환이 가능하게 만드는 행동 디자인 패턴입니다.

원래 객체는 콘텍스트라고 불리며 전략 객체에 대한 참조를 포함합니다. 콘텍스트는 행동의 실행을 연결된 전략 객체에 위임합니다. 콘텍스트가 작업을 수행하는 방식을 변경하기 위하여 다른 객체들은 현재 연결된 전략 객체를 다른 전략 객체와 대체할 수 있습니다.

내비게이션
 소개
 개념적인 예시
 index
 Output
 실제 사례 예시
 index
 Output

복잡도:

인기도:

사용 예시: 전략 패턴은 PHP 코드에서 특히 런타임에 알고리즘을 전환해야 하는 경우 자주 사용됩니다. 그러나 이 패턴은 2009년 PHP 5.3에 도입된 익명 함수라는 강력한 대안이 있습니다.

식별: 전략 패턴은 중첩된 객체가 실제 작업을 수행할 수 있도록 하는 메서드가 있으며 또 해당 객체를 다른 객체로 대체할 수 있는 세터가 있습니다.

개념적인 예시

이 예시는 전략 패턴의 구조를 보여주고 다음 질문에 중점을 둡니다:

  • 패턴은 어떤 클래스들로 구성되어 있나요?
  • 이 클래스들은 어떤 역할을 하나요?
  • 패턴의 요소들은 어떻게 서로 연관되어 있나요?

이 패턴의 구조를 배우면 실제 PHP 사용 사례를 기반으로 하는 다음 예시를 더욱 쉽게 이해할 수 있을 것입니다.

index.php: 개념적인 예시

<?php

namespace RefactoringGuru\Strategy\Conceptual;

/**
 * The Context defines the interface of interest to clients.
 */
class Context
{
    /**
     * @var Strategy The Context maintains a reference to one of the Strategy
     * objects. The Context does not know the concrete class of a strategy. It
     * should work with all strategies via the Strategy interface.
     */
    private $strategy;

    /**
     * Usually, the Context accepts a strategy through the constructor, but also
     * provides a setter to change it at runtime.
     */
    public function __construct(Strategy $strategy)
    {
        $this->strategy = $strategy;
    }

    /**
     * Usually, the Context allows replacing a Strategy object at runtime.
     */
    public function setStrategy(Strategy $strategy)
    {
        $this->strategy = $strategy;
    }

    /**
     * The Context delegates some work to the Strategy object instead of
     * implementing multiple versions of the algorithm on its own.
     */
    public function doSomeBusinessLogic(): void
    {
        // ...

        echo "Context: Sorting data using the strategy (not sure how it'll do it)\n";
        $result = $this->strategy->doAlgorithm(["a", "b", "c", "d", "e"]);
        echo implode(",", $result) . "\n";

        // ...
    }
}

/**
 * The Strategy interface declares operations common to all supported versions
 * of some algorithm.
 *
 * The Context uses this interface to call the algorithm defined by Concrete
 * Strategies.
 */
interface Strategy
{
    public function doAlgorithm(array $data): array;
}

/**
 * Concrete Strategies implement the algorithm while following the base Strategy
 * interface. The interface makes them interchangeable in the Context.
 */
class ConcreteStrategyA implements Strategy
{
    public function doAlgorithm(array $data): array
    {
        sort($data);

        return $data;
    }
}

class ConcreteStrategyB implements Strategy
{
    public function doAlgorithm(array $data): array
    {
        rsort($data);

        return $data;
    }
}

/**
 * The client code picks a concrete strategy and passes it to the context. The
 * client should be aware of the differences between strategies in order to make
 * the right choice.
 */
$context = new Context(new ConcreteStrategyA());
echo "Client: Strategy is set to normal sorting.\n";
$context->doSomeBusinessLogic();

echo "\n";

echo "Client: Strategy is set to reverse sorting.\n";
$context->setStrategy(new ConcreteStrategyB());
$context->doSomeBusinessLogic();

Output.txt: 실행 결과

Client: Strategy is set to normal sorting.
Context: Sorting data using the strategy (not sure how it'll do it)
a,b,c,d,e

Client: Strategy is set to reverse sorting.
Context: Sorting data using the strategy (not sure how it'll do it)
e,d,c,b,a

실제 사례 예시

이 예시에서 전략 패턴은 전자 상거래 앱의 지불 메서드들을 나타내는 데 사용됩니다.

각 결제 수단은 특정 결제 양식을 표시하여 사용자로부터 적절한 결제 내역을 수집하고 결제 처리 회사에 보낼 수 있습니다. 그런 다음 결제 처리 회사는 사용자를 당사 웹사이트로 다시 리다이렉트 합니다. 그 후 결제 메서드는 반환된 매개변수들을 확인하여 주문 완료 여부를 확인합니다.

index.php: 실제 사례 예시

<?php

namespace RefactoringGuru\Strategy\RealWorld;

/**
 * This is the router and controller of our application. Upon receiving a
 * request, this class decides what behavior should be executed. When the app
 * receives a payment request, the OrderController class also decides which
 * payment method it should use to process the request. Thus, the class acts as
 * the Context and the Client at the same time.
 */
class OrderController
{
    /**
     * Handle POST requests.
     *
     * @param $url
     * @param $data
     * @throws \Exception
     */
    public function post(string $url, array $data)
    {
        echo "Controller: POST request to $url with " . json_encode($data) . "\n";

        $path = parse_url($url, PHP_URL_PATH);

        if (preg_match('#^/orders?$#', $path, $matches)) {
            $this->postNewOrder($data);
        } else {
            echo "Controller: 404 page\n";
        }
    }

    /**
     * Handle GET requests.
     *
     * @param $url
     * @throws \Exception
     */
    public function get(string $url): void
    {
        echo "Controller: GET request to $url\n";

        $path = parse_url($url, PHP_URL_PATH);
        $query = parse_url($url, PHP_URL_QUERY);
        parse_str($query, $data);

        if (preg_match('#^/orders?$#', $path, $matches)) {
            $this->getAllOrders();
        } elseif (preg_match('#^/order/([0-9]+?)/payment/([a-z]+?)(/return)?$#', $path, $matches)) {
            $order = Order::get($matches[1]);

            // The payment method (strategy) is selected according to the value
            // passed along with the request.
            $paymentMethod = PaymentFactory::getPaymentMethod($matches[2]);

            if (!isset($matches[3])) {
                $this->getPayment($paymentMethod, $order, $data);
            } else {
                $this->getPaymentReturn($paymentMethod, $order, $data);
            }
        } else {
            echo "Controller: 404 page\n";
        }
    }

    /**
     * POST /order {data}
     */
    public function postNewOrder(array $data): void
    {
        $order = new Order($data);
        echo "Controller: Created the order #{$order->id}.\n";
    }

    /**
     * GET /orders
     */
    public function getAllOrders(): void
    {
        echo "Controller: Here's all orders:\n";
        foreach (Order::get() as $order) {
            echo json_encode($order, JSON_PRETTY_PRINT) . "\n";
        }
    }

    /**
     * GET /order/123/payment/XX
     */
    public function getPayment(PaymentMethod $method, Order $order, array $data): void
    {
        // The actual work is delegated to the payment method object.
        $form = $method->getPaymentForm($order);
        echo "Controller: here's the payment form:\n";
        echo $form . "\n";
    }

    /**
     * GET /order/123/payment/XXX/return?key=AJHKSJHJ3423&success=true
     */
    public function getPaymentReturn(PaymentMethod $method, Order $order, array $data): void
    {
        try {
            // Another type of work delegated to the payment method.
            if ($method->validateReturn($order, $data)) {
                echo "Controller: Thanks for your order!\n";
                $order->complete();
            }
        } catch (\Exception $e) {
            echo "Controller: got an exception (" . $e->getMessage() . ")\n";
        }
    }
}

/**
 * A simplified representation of the Order class.
 */
class Order
{
    /**
     * For the sake of simplicity, we'll store all created orders here...
     *
     * @var array
     */
    private static $orders = [];

    /**
     * ...and access them from here.
     *
     * @param int $orderId
     * @return mixed
     */
    public static function get(int $orderId = null)
    {
        if ($orderId === null) {
            return static::$orders;
        } else {
            return static::$orders[$orderId];
        }
    }

    /**
     * The Order constructor assigns the values of the order's fields. To keep
     * things simple, there is no validation whatsoever.
     *
     * @param array $attributes
     */
    public function __construct(array $attributes)
    {
        $this->id = count(static::$orders);
        $this->status = "new";
        foreach ($attributes as $key => $value) {
            $this->{$key} = $value;
        }
        static::$orders[$this->id] = $this;
    }

    /**
     * The method to call when an order gets paid.
     */
    public function complete(): void
    {
        $this->status = "completed";
        echo "Order: #{$this->id} is now {$this->status}.";
    }
}

/**
 * This class helps to produce a proper strategy object for handling a payment.
 */
class PaymentFactory
{
    /**
     * Get a payment method by its ID.
     *
     * @param $id
     * @return PaymentMethod
     * @throws \Exception
     */
    public static function getPaymentMethod(string $id): PaymentMethod
    {
        switch ($id) {
            case "cc":
                return new CreditCardPayment();
            case "paypal":
                return new PayPalPayment();
            default:
                throw new \Exception("Unknown Payment Method");
        }
    }
}

/**
 * The Strategy interface describes how a client can use various Concrete
 * Strategies.
 *
 * Note that in most examples you can find on the Web, strategies tend to do
 * some tiny thing within one method. However, in reality, your strategies can
 * be much more robust (by having several methods, for example).
 */
interface PaymentMethod
{
    public function getPaymentForm(Order $order): string;

    public function validateReturn(Order $order, array $data): bool;
}

/**
 * This Concrete Strategy provides a payment form and validates returns for
 * credit card payments.
 */
class CreditCardPayment implements PaymentMethod
{
    static private $store_secret_key = "swordfish";

    public function getPaymentForm(Order $order): string
    {
        $returnURL = "https://our-website.com/" .
            "order/{$order->id}/payment/cc/return";

        return <<<FORM
<form action="https://my-credit-card-processor.com/charge" method="POST">
    <input type="hidden" id="email" value="{$order->email}">
    <input type="hidden" id="total" value="{$order->total}">
    <input type="hidden" id="returnURL" value="$returnURL">
    <input type="text" id="cardholder-name">
    <input type="text" id="credit-card">
    <input type="text" id="expiration-date">
    <input type="text" id="ccv-number">
    <input type="submit" value="Pay">
</form>
FORM;
    }

    public function validateReturn(Order $order, array $data): bool
    {
        echo "CreditCardPayment: ...validating... ";

        if ($data['key'] != md5($order->id . static::$store_secret_key)) {
            throw new \Exception("Payment key is wrong.");
        }

        if (!isset($data['success']) || !$data['success'] || $data['success'] == 'false') {
            throw new \Exception("Payment failed.");
        }

        // ...

        if (floatval($data['total']) < $order->total) {
            throw new \Exception("Payment amount is wrong.");
        }

        echo "Done!\n";

        return true;
    }
}

/**
 * This Concrete Strategy provides a payment form and validates returns for
 * PayPal payments.
 */
class PayPalPayment implements PaymentMethod
{
    public function getPaymentForm(Order $order): string
    {
        $returnURL = "https://our-website.com/" .
            "order/{$order->id}/payment/paypal/return";

        return <<<FORM
<form action="https://paypal.com/payment" method="POST">
    <input type="hidden" id="email" value="{$order->email}">
    <input type="hidden" id="total" value="{$order->total}">
    <input type="hidden" id="returnURL" value="$returnURL">
    <input type="submit" value="Pay on PayPal">
</form>
FORM;
    }

    public function validateReturn(Order $order, array $data): bool
    {
        echo "PayPalPayment: ...validating... ";

        // ...

        echo "Done!\n";

        return true;
    }
}

/**
 * The client code.
 */

$controller = new OrderController();

echo "Client: Let's create some orders\n";

$controller->post("/orders", [
    "email" => "me@example.com",
    "product" => "ABC Cat food (XL)",
    "total" => 9.95,
]);

$controller->post("/orders", [
    "email" => "me@example.com",
    "product" => "XYZ Cat litter (XXL)",
    "total" => 19.95,
]);

echo "\nClient: List my orders, please\n";

$controller->get("/orders");

echo "\nClient: I'd like to pay for the second, show me the payment form\n";

$controller->get("/order/1/payment/paypal");

echo "\nClient: ...pushes the Pay button...\n";
echo "\nClient: Oh, I'm redirected to the PayPal.\n";
echo "\nClient: ...pays on the PayPal...\n";
echo "\nClient: Alright, I'm back with you, guys.\n";

$controller->get("/order/1/payment/paypal/return" .
    "?key=c55a3964833a4b0fa4469ea94a057152&success=true&total=19.95");

Output.txt: 실행 결과

Client: Let's create some orders
Controller: POST request to /orders with {"email":"me@example.com","product":"ABC Cat food (XL)","total":9.95}
Controller: Created the order #0.
Controller: POST request to /orders with {"email":"me@example.com","product":"XYZ Cat litter (XXL)","total":19.95}
Controller: Created the order #1.

Client: List my orders, please
Controller: GET request to /orders
Controller: Here's all orders:
{
    "id": 0,
    "status": "new",
    "email": "me@example.com",
    "product": "ABC Cat food (XL)",
    "total": 9.95
}
{
    "id": 1,
    "status": "new",
    "email": "me@example.com",
    "product": "XYZ Cat litter (XXL)",
    "total": 19.95
}

Client: I'd like to pay for the second, show me the payment form
Controller: GET request to /order/1/payment/paypal
Controller: here's the payment form:
<form action="https://paypal.com/payment" method="POST">
    <input type="hidden" id="email" value="me@example.com">
    <input type="hidden" id="total" value="19.95">
    <input type="hidden" id="returnURL" value="https://our-website.com/order/1/payment/paypal/return">
    <input type="submit" value="Pay on PayPal">
</form>

Client: ...pushes the Pay button...

Client: Oh, I'm redirected to the PayPal.

Client: ...pays on the PayPal...

Client: Alright, I'm back with you, guys.
Controller: GET request to /order/1/payment/paypal/return?key=c55a3964833a4b0fa4469ea94a057152&success=true&total=19.95
PayPalPayment: ...validating... Done!
Controller: Thanks for your order!
Order: #1 is now completed.

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