Django Signals Home

Django signals provide a powerful way to decouple certain parts of your application by allowing components to communicate without being directly dependent on each other. Signals are particularly useful when you want to notify certain parts of your code that some action has taken place elsewhere in the system.

A signal is simply a message that is sent when an event occurs, and listeners (known as receivers) can be connected to respond to these signals. This mechanism allows for a more flexible and scalable codebase by avoiding tight coupling between different components of the application.

Key Concepts

• Sender: The component that triggers the signal. It could be a model, a form, or any part of your application that needs to notify others when an event happens.
• Receiver: The function that gets notified when the signal is sent. This function performs specific actions in response to the signal.
• Signal: A predefined or custom event that can be sent by the sender. In Django, signals are available for various model lifecycle events like saving or deleting an object.

When to Use Django Signals

Signals are typically used in scenarios where you need to perform some actions when a particular event occurs, but you don't want to directly embed that logic into the component responsible for triggering the event. Common use cases for signals include:

• Automatically creating related records when a model is saved (using the post_save signal).   
• Cleaning up or archiving records when a model is deleted (using the pre_delete or post_delete signals).
• Tracking changes to a model or sending notifications when specific events occur.

Explore Django Signals   

• What are Django Signals?
• How Signals work
• Built-in Signals
• Creating Custom Signals
• Connecting Signals to Receivers
• Best Practices for Using Signals

Built-in Signals

Django comes with several built-in signals, which can be used to hook into various stages of model lifecycles, form processing, and request handling. Some of the most commonly used built-in signals include:   

• pre_save: Sent just before a model's save() method is called.
• post_save: Sent just after a model's save() method is called.
• pre_delete: Sent before a model's delete() method is called.
• post_delete: Sent after a model's delete() method is called.

Custom Signals

In addition to the built-in signals, Django allows developers to create their own custom signals. This is useful when you need to define custom events within your application that other components might be interested in. For example, you might want to send a signal when a user completes a specific action or when a background task finishes.

Overall, Django signals are a flexible tool that can help you build more modular and maintainable applications by keeping different parts of your codebase loosely coupled.