Django signals are a powerful tool for achieving decoupling, allowing other parts of the code to be notified of certain events that occur. Signals are primarily used to pass information between different parts of a Django application, especially when model operations occur. This article takes a deep dive into how Django signals work, how to define and receive them, and how to use them effectively in your projects.
1. Basic concepts of Django signals
Django signals are a mechanism for implementing the publish-subscribe pattern. In this mode, the sender does not need to know the specific information of the receiver. It only needs to declare that events occur, and the receiver can listen and respond to these events.
2. Commonly used Django built-in signals
Django provides a series of built-in signals that cover common ORM events such as model save and delete.
django.db.models.signals.pre_save: Sent before the object is saved.django.db.models.signals.post_save: Sent after the object is saved.django.db.models.signals.pre_delete: Sent before object deletion.django.db.models.signals.post_delete: Sent after object deletion.
3. Define and send custom signals
In addition to using Django's built-in signals, you can also create custom signals.
Example: Define a signal named new_user_registered.
from django.dispatch import Signal
# 定义信号
new_user_registered = Signal(providing_args=["user"