from collections import deque
from eventsourcing.domain.model.entity import TimestampedVersionedEntity
from eventsourcing.domain.model.events import publish
[docs]class AggregateRoot(TimestampedVersionedEntity):
"""
Root entity for an aggregate in a domain driven design.
"""
[docs] class Event(TimestampedVersionedEntity.Event):
"""Layer supertype."""
[docs] class Created(Event, TimestampedVersionedEntity.Created):
"""Published when an AggregateRoot is created."""
[docs] class AttributeChanged(Event, TimestampedVersionedEntity.AttributeChanged):
"""Published when an AggregateRoot is changed."""
[docs] class Discarded(Event, TimestampedVersionedEntity.Discarded):
"""Published when an AggregateRoot is discarded."""
def __init__(self, **kwargs):
super(AggregateRoot, self).__init__(**kwargs)
self._pending_events = deque()
def _publish(self, event):
"""
Appends event to internal collection of pending events.
"""
self._pending_events.append(event)
[docs] def save(self):
"""
Publishes pending events for others in application.
"""
batch_of_events = []
try:
while True:
batch_of_events.append(self._pending_events.popleft())
except IndexError:
pass
if batch_of_events:
publish(batch_of_events)