spakky-domain 6.1.2

DDD building blocks for Spakky Framework (Entity, AggregateRoot, ValueObject, DomainEvent, CQRS)

Spakky DDD

Domain-Driven Design building blocks for Spakky Framework.

Installation

pip install spakky-domain

Features

• Entities: Objects with unique identity and lifecycle
• Value Objects: Immutable objects compared by attributes
• Aggregate Roots: Consistency boundaries with event management
• Domain Events: Immutable events for event-driven architecture
• CQRS: Command and Query use case abstractions

Quick Start

Entity

Entities are objects with a unique identity that persists over time:

from uuid import UUID, uuid4

from spakky.core.common.mutability import mutable
from spakky.domain.models.entity import AbstractEntity


@mutable
class User(AbstractEntity[UUID]):
    name: str
    email: str

    @classmethod
    def next_id(cls) -> UUID:
        return uuid4()

    def validate(self) -> None:
        if not self.email:
            raise ValueError("Email is required")

Value Object

Value Objects are immutable and compared by their attributes:

from spakky.core.common.mutability import immutable
from spakky.domain.models.value_object import AbstractValueObject


@immutable
class Money(AbstractValueObject):
    amount: int
    currency: str

    def validate(self) -> None:
        if self.amount < 0:
            raise ValueError("Amount cannot be negative")

Aggregate Root

Aggregate Roots are entities that manage domain events:

from uuid import UUID, uuid4

from spakky.core.common.mutability import mutable, immutable
from spakky.domain.models.aggregate_root import AbstractAggregateRoot
from spakky.domain.models.event import AbstractDomainEvent


@immutable
class OrderCreatedEvent(AbstractDomainEvent):
    order_id: UUID
    customer_id: UUID


@mutable
class Order(AbstractAggregateRoot[UUID]):
    customer_id: UUID
    total: int

    @classmethod
    def next_id(cls) -> UUID:
        return uuid4()

    def validate(self) -> None:
        if self.total < 0:
            raise ValueError("Total cannot be negative")

    @classmethod
    def create(cls, customer_id: UUID, total: int) -> "Order":
        order = cls(uid=cls.next_id(), customer_id=customer_id, total=total)
        order.add_event(OrderCreatedEvent(order_id=order.uid, customer_id=customer_id))
        return order

Domain Events

Domain events represent state changes in the domain:

from spakky.core.common.mutability import immutable
from spakky.domain.models.event import AbstractDomainEvent, AbstractIntegrationEvent


# Internal domain event
@immutable
class UserRegistered(AbstractDomainEvent):
    user_id: str
    email: str


# Cross-boundary integration event
@immutable
class UserRegisteredIntegration(AbstractIntegrationEvent):
    user_id: str
    email: str

CQRS Use Cases

Separate read and write operations.

Key Principles:

• Commands: Use Repository for domain aggregate persistence
• Queries: Implement directly using ORM/SQL (do NOT add query methods to Repository)
• This separation prevents domain pollution by keeping query concerns out of the domain layer

from uuid import UUID

from spakky.core.common.mutability import immutable
from spakky.domain.application.command import AbstractCommand, IAsyncCommandUseCase
from spakky.domain.application.query import AbstractQuery, IAsyncQueryUseCase


# Command
@immutable
class CreateUserCommand(AbstractCommand):
    name: str
    email: str


class CreateUserUseCase(IAsyncCommandUseCase[CreateUserCommand, UUID]):
    async def run(self, command: CreateUserCommand) -> UUID:
        # Business logic here
        ...


# Query
@immutable
class GetUserQuery(AbstractQuery):
    user_id: UUID


class GetUserUseCase(IAsyncQueryUseCase[GetUserQuery, User | None]):
    async def run(self, query: GetUserQuery) -> User | None:
        # Business logic here
        ...

API Reference

Models

Class	Description
AbstractEntity[T]	Base class for entities with identity type T
AbstractAggregateRoot[T]	Entity that manages domain events
AbstractValueObject	Immutable value object
AbstractEvent	Base class for all events
AbstractDomainEvent	Domain events (within bounded context)
AbstractIntegrationEvent	Integration events (cross-boundary)

Application

Class	Description
AbstractCommand	Base class for command DTOs
AbstractQuery	Base class for query DTOs
ICommandUseCase	Sync command use case interface
IAsyncCommandUseCase	Async command use case interface
IQueryUseCase	Sync query use case interface
IAsyncQueryUseCase	Async query use case interface

Related Packages

Package	Description
spakky-data	Repository and transaction abstractions
spakky-event	Event publisher/consumer interfaces and @EventHandler stereotype

License

MIT License