Strategic architecture, tactical design, and testable code principles (SOLID, Clean Architecture, Design Patterns, Testable Design)
97
97%
Does it follow best practices?
Impact
Pending
No eval scenarios have been run
Passed
No known issues
ORM-specific code (entities, mappings, queries) belongs in the infrastructure layer. The domain and application layers should not know which ORM (or if any ORM) is being used.
Incorrect (ORM in application layer):
# application/usecases/get_orders.py
from sqlalchemy.orm import Session, joinedload
from sqlalchemy import and_, or_
class GetOrdersUseCase:
def __init__(self, session: Session): # SQLAlchemy session in use case
self.session = session
def execute(self, customer_id: str, filters: OrderFilters):
# SQLAlchemy query in use case
query = self.session.query(Order).options(
joinedload(Order.items),
joinedload(Order.customer)
)
if filters.status:
query = query.filter(Order.status == filters.status)
if filters.date_range:
query = query.filter(and_(
Order.created_at >= filters.date_range.start,
Order.created_at <= filters.date_range.end
))
return query.order_by(Order.created_at.desc()).all()
# Use case is now coupled to SQLAlchemy
# Switching to Peewee or raw SQL requires rewriting use caseCorrect (ORM isolated in infrastructure):
# application/ports/order_repository.py
from abc import ABC, abstractmethod
class OrderRepository(ABC):
@abstractmethod
def find_by_customer(
self,
customer_id: CustomerId,
filters: OrderFilters
) -> list[Order]:
pass
# application/usecases/get_orders.py
class GetOrdersUseCase:
def __init__(self, orders: OrderRepository): # Interface, not Session
self.orders = orders
def execute(self, customer_id: str, filters: OrderFilters) -> list[Order]:
return self.orders.find_by_customer(
CustomerId(customer_id),
filters
)
# infrastructure/persistence/sqlalchemy_order_repository.py
from sqlalchemy.orm import Session, joinedload
class SqlAlchemyOrderRepository(OrderRepository):
def __init__(self, session: Session):
self.session = session
def find_by_customer(
self,
customer_id: CustomerId,
filters: OrderFilters
) -> list[Order]:
query = self.session.query(OrderEntity).options(
joinedload(OrderEntity.items)
).filter(OrderEntity.customer_id == customer_id.value)
if filters.status:
query = query.filter(OrderEntity.status == filters.status.value)
entities = query.order_by(OrderEntity.created_at.desc()).all()
return [self._to_domain(e) for e in entities]
def _to_domain(self, entity: OrderEntity) -> Order:
# Map ORM entity to domain entity
passBenefits:
Reference: Repository Pattern
clean-architecture
evals
references
design-patterns
solid-principles
testable-design