PHP 策略模式讲解和代码示例

<?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 { private static $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"); 

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.