Signals

Django-style signals for model lifecycle events.

Available Signals

from p8s.db.signals import Signal

Signal.PRE_SAVE      # Before create/update
Signal.POST_SAVE     # After create/update
Signal.PRE_DELETE    # Before delete
Signal.POST_DELETE   # After delete
Signal.POST_INIT     # After model init
Signal.M2M_CHANGED   # Many-to-many change

Connecting Handlers

Using @receiver Decorator

from p8s.db.signals import Signal, receiver

@receiver(Signal.POST_SAVE, sender=Product)
def on_product_save(sender, instance, created, **kwargs):
    if created:
        print(f"New product: {instance.name}")
    else:
        print(f"Updated: {instance.name}")

@receiver(Signal.PRE_DELETE, sender=Product)
def on_product_delete(sender, instance, **kwargs):
    print(f"Deleting: {instance.name}")

Manual Connection

from p8s.db.signals import connect, disconnect

def my_handler(sender, **kwargs):
    ...

connect(Signal.POST_SAVE, my_handler, sender=Product)
disconnect(Signal.POST_SAVE, my_handler, sender=Product)

Sending Signals

Signals are automatically sent by CRUDBase operations. For manual sending:

from p8s.db.signals import send, send_async

# Sync
send(Signal.POST_SAVE, sender=Product, instance=product, created=True)

# Async
await send_async(Signal.POST_SAVE, sender=Product, instance=product, created=True)

Handler Arguments

Signal	Arguments
PRE_SAVE	sender, instance
POST_SAVE	sender, instance, created
PRE_DELETE	sender, instance
POST_DELETE	sender, instance