التجميعات والمستودعات والمصانع

حماية الثوابت

ما هو التجميع

الجذر يحمي التجميع بأكمله

<?php
final class LineItem {
    public function __construct(
        public readonly string $sku,
        public readonly int $qty,
        public readonly int $unitCents
    ) {}
    public function subtotal(): int { return $this->qty * $this->unitCents; }
}

final class Order { // Aggregate Root
    /** @var LineItem[] */
    private array $items = [];
    public function __construct(public readonly string $id) {}

    public function addItem(string $sku, int $qty, int $unitCents): void {
        if ($qty < 1) { throw new DomainException('qty must be >= 1'); }
        $this->items[] = new LineItem($sku, $qty, $unitCents);
    }
    public function total(): int {
        return array_sum(array_map(fn(LineItem $i) => $i->subtotal(), $this->items));
    }
}
$o = new Order('o1');
$o->addItem('A', 2, 500);
$o->addItem('B', 1, 300);
echo $o->total(), PHP_EOL; // 1300

تصميم تجميعات صغيرة

الإشارة باستخدام المعرّف

<?php
final class CustomerId {
    public function __construct(public readonly string $value) {}
}
final class Order {
    public function __construct(
        public readonly string $id,
        public readonly CustomerId $customerId // reference, not object
    ) {}
}
$order = new Order('o1', new CustomerId('cus_99'));
echo $order->customerId->value, PHP_EOL;

عقد المستودع

<?php
interface OrderRepository {
    public function ofId(string $id): ?Order;
    public function save(Order $order): void;
    public function nextIdentity(): string;
}

تطبيق داخل الذاكرة

<?php
interface OrderRepository {
    public function ofId(string $id): ?object;
    public function save(object $order): void;
    public function nextIdentity(): string;
}
final class Order { public function __construct(public readonly string $id) {} }

final class InMemoryOrderRepository implements OrderRepository {
    private array $store = [];
    public function ofId(string $id): ?object { return $this->store[$id] ?? null; }
    public function save(object $order): void { $this->store[$order->id] = $order; }
    public function nextIdentity(): string { return 'o_' . bin2hex(random_bytes(4)); }
}
$repo = new InMemoryOrderRepository();
$repo->save(new Order('o1'));
var_dump($repo->ofId('o1') !== null);

المستودع ليس DAO

المصانع للإنشاء المعقّد

<?php
final class Order {
    private function __construct(
        public readonly string $id,
        public readonly string $customerId
    ) {}
    public static function place(string $customerId): self {
        if ($customerId === '') { throw new DomainException('customer required'); }
        return new self('o_' . bin2hex(random_bytes(4)), $customerId);
    }
}
$order = Order::place('cus_1');
echo $order->id, PHP_EOL;

كيف تتعاون معًا

فرض ثابت على مستوى التجميع بأكمله

<?php
final class Order {
    private array $items = [];
    public function __construct(
        public readonly string $id,
        private int $creditLimitCents
    ) {}
    public function addItem(int $cents): void {
        if ($this->total() + $cents > $this->creditLimitCents) {
            throw new DomainException('Exceeds credit limit');
        }
        $this->items[] = $cents;
    }
    public function total(): int { return array_sum($this->items); }
}
$o = new Order('o1', 1000);
$o->addItem(600);
try { $o->addItem(600); } catch (DomainException $e) { echo $e->getMessage(), PHP_EOL; }
echo $o->total(), PHP_EOL; // 600

اختبار سريع

مراجعة