รูปแบบโครงสร้าง: Adapter, Decorator, Facade

การประกอบอ็อบเจกต์

อะแดปเตอร์: ปัญหา

<?php
// What our app wants to depend on
interface PaymentGateway { public function pay(float $dollars): string; }

// What the vendor actually gives us (cents, array result)
final class StripeSdk {
    public function chargeCard(int $cents): array {
        return ['id' => 'ch_1', 'amount' => $cents];
    }
}
// dollars vs cents, string vs array -> shapes don't line up
var_dump((new StripeSdk())->chargeCard(2000));

อะแดปเตอร์ในโค้ด

<?php
interface PaymentGateway { public function pay(float $dollars): string; }

// Third-party SDK with an incompatible API
final class StripeSdk {
    public function chargeCard(int $cents): array {
        return ['id' => 'ch_1', 'amount' => $cents];
    }
}

final class StripeAdapter implements PaymentGateway {
    public function __construct(private StripeSdk $sdk) {}
    public function pay(float $dollars): string {
        $res = $this->sdk->chargeCard((int) round($dollars * 100));
        return "charged {$res['amount']}c -> {$res['id']}";
    }
}
echo (new StripeAdapter(new StripeSdk()))->pay(20.0), PHP_EOL;

เดคอเรเตอร์: แนวคิด

<?php
interface Coffee { public function cost(): float; }
final class Espresso implements Coffee {
    public function cost(): float { return 2.0; }
}
final class WithMilk implements Coffee {
    public function __construct(private Coffee $inner) {}
    public function cost(): float { return $this->inner->cost() + 0.5; }
}
echo (new WithMilk(new Espresso()))->cost(), PHP_EOL; // 2.5

เดคอเรเตอร์ในโค้ด

<?php
interface DataSource { public function read(): string; }

final class FileSource implements DataSource {
    public function read(): string { return 'raw-data'; }
}

final class UpperCaseDecorator implements DataSource {
    public function __construct(private DataSource $inner) {}
    public function read(): string { return strtoupper($this->inner->read()); }
}
final class ExclaimDecorator implements DataSource {
    public function __construct(private DataSource $inner) {}
    public function read(): string { return $this->inner->read() . '!!!'; }
}

$src = new ExclaimDecorator(new UpperCaseDecorator(new FileSource()));
echo $src->read(), PHP_EOL; // RAW-DATA!!!

เดคอเรเตอร์ในโลกจริง

เดคอเรเตอร์กับการสืบทอด

ฟาซาด: แนวคิด

<?php
// Without a facade, the client wires every step itself
final class Cpu { public function boot(): string { return 'cpu '; } }
final class Disk { public function load(): string { return 'disk '; } }
final class Ram { public function check(): string { return 'ram'; } }

$out = (new Cpu())->boot() . (new Disk())->load() . (new Ram())->check();
echo $out, PHP_EOL; // cpu disk ram

ฟาซาดในโค้ด

<?php
final class Inventory { public function reserve(string $sku): bool { return true; } }
final class Payments { public function charge(float $amt): bool { return true; } }
final class Shipping { public function dispatch(string $sku): string { return 'tracking-99'; } }

final class OrderFacade {
    public function __construct(
        private Inventory $inv,
        private Payments $pay,
        private Shipping $ship
    ) {}
    public function place(string $sku, float $amount): string {
        if (!$this->inv->reserve($sku)) { return 'out of stock'; }
        if (!$this->pay->charge($amount)) { return 'payment failed'; }
        return 'shipped: ' . $this->ship->dispatch($sku);
    }
}
echo (new OrderFacade(new Inventory(), new Payments(), new Shipping()))
    ->place('ABC', 49.99), PHP_EOL;

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