Class DomainServiceAbstract

Base class for Domain Services in Domain-Driven Design.

Domain Services encapsulate domain logic that:

• Doesn't naturally fit within an Entity or Value Object
• Operates on multiple aggregates
• Represents a significant process or transformation in the domain

Unlike Application Services, Domain Services contain pure domain logic and have no dependencies on infrastructure concerns.

class MoneyTransferService extends DomainService {
  readonly name = 'MoneyTransferService';

  transfer(
    from: BankAccount,
    to: BankAccount,
    amount: Money
  ): Result<void, DomainError> {
    // Validate transfer
    if (!from.canWithdraw(amount)) {
      return Result.fail(
        new DomainError('INSUFFICIENT_FUNDS', 'Account has insufficient funds')
      );
    }

    if (!from.currency.equals(amount.currency)) {
      return Result.fail(
        new DomainError('CURRENCY_MISMATCH', 'Currency mismatch')
      );
    }

    // Perform transfer
    from.withdraw(amount);
    to.deposit(amount);

    // Record domain events
    from.record({
      occurredAt: new Date(),
      accountId: from.id.value,
      amount: amount.value,
      type: 'withdrawal'
    });

    to.record({
      occurredAt: new Date(),
      accountId: to.id.value,
      amount: amount.value,
      type: 'deposit'
    });

    return Result.ok(undefined);
  }
}
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class OrderPricingService extends DomainService {
  readonly name = 'OrderPricingService';

  calculateTotal(order: Order, customer: Customer): Money {
    let total = order.subtotal;

    // Apply customer discount
    if (customer.isPremium()) {
      total = total.multiply(0.9); // 10% discount
    }

    // Add shipping
    const shipping = this.calculateShipping(order, customer);
    total = total.add(shipping);

    // Add taxes
    const tax = this.calculateTax(total, customer.address);
    total = total.add(tax);

    return total;
  }

  private calculateShipping(order: Order, customer: Customer): Money {
    // Shipping logic
  }

  private calculateTax(amount: Money, address: Address): Money {
    // Tax calculation logic
  }
}
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