Nima agregat?

Obyektga asoslangan dizaynda (DDD) agregat, ma'lumotlarning yaxlitligini ta'minlash uchun birgalikda bog'langan ob'ektlar klasteridir. Har bir agregatning ildiz ob'ekti (Aggregat Root) bo'lib, u agregat ichidagi boshqa ob'ektlarga kirish uchun yagona nuqtadir. Agregat ichidagi barcha o'zgarishlar invariants (integrity qoidalari)ni saqlash uchun ildiz ob'ekti orqali amalga oshirilishi kerak.

Asosiy xususiyatlar:

• Ildiz ob'ekt (Aggregat Root): Agregat komponentlariga kirish uchun yagona nuqta.
• Kapsüllash: Agregat ichidagi ichki ob'ektlar tashqaridan to'g'ridan-to'g'ri kirish uchun mo'ljallanmagan.
• Barqarorlik chegarasi: Agregat invariantslarni saqlash uchun chegarani belgilaydi. Agregat ichidagi o'zgarishlar tranzaktsion ravishda barqarordir.
• Izolyatsiya: Boshqa agregat ob'ektlari bilan to'g'ridan-to'g'ri muloqot qilish mumkin emas, faqat ildiz ob'ektlari yoki domen xizmatlari orqali.

Misol:

<?php

// "Buyurtma" agregatining ildiz ob'ekti
class Order
{
    private OrderId $id;
    private CustomerId $customerId;
    /** @var OrderItem[] */
    private array $items = [];
    private OrderStatus $status;

    public function __construct(OrderId $id, CustomerId $customerId)
    {
        $this->id = $id;
        $this->customerId = $customerId;
        $this->status = OrderStatus::Pending;
    }

    public function addItem(ProductId $productId, int $quantity, Money $price): void
    {
        // invariants tekshiruvi, masalan, miqdor > 0
        if ($quantity <= 0) {
            throw new InvalidArgumentException("Miqdor 0 dan katta bo'lishi kerak.");
        }

        $this->items[] = new OrderItem($productId, $quantity, $price);
    }

    public function confirm(): void
    {
        // Statusni o'zgartirishdan oldin invariantsni tekshirish
        if ($this->status !== OrderStatus::Pending) {
            throw new DomainException("Buyurtma 'Kutish' holatida emas.");
        }

        // Tasdiqlash logikasi, masalan, tovar mavjudligini tekshirish
        $this->status = OrderStatus::Confirmed;
    }

    public function getId(): OrderId
    {
        return $this->id;
    }

    public function getStatus(): OrderStatus
    {
        return $this->status;
    }

    /** @return OrderItem[] */
    public function getItems(): array
    {
        return $this->items;
    }
}

// "Buyurtma satri" ichki ob'ekti
class OrderItem
{
    private ProductId $productId;
    private int $quantity;
    private Money $price;

    public function __construct(ProductId $productId, int $quantity, Money $price)
    {
        $this->productId = $productId;
        $this->quantity = $quantity;
        $this->price = $price;
    }

    public function getProductId(): ProductId
    {
        return $this->productId;
    }

    public function getQuantity(): int
    {
        return $this->quantity;
    }

    public function getPrice(): Money
    {
        return $this->price;
    }
}

// Qiymat ob'ektlari (misol uchun)
final class OrderId {}
final class CustomerId {}
final class ProductId {}
final class Money {}
enum OrderStatus { case Pending; case Confirmed; case Cancelled; }