Receiver decorator in Django - Mini Project: Build & Apply

Using the Receiver Decorator in Django Signals

📖 Scenario: You are building a Django app where you want to perform an action automatically whenever a new user is created. Django signals help you do this by letting you run code when certain events happen.

🎯 Goal: Learn how to use the @receiver decorator to connect a function to Django's post_save signal for the User model. This function will print a welcome message whenever a new user is saved.

📋 What You'll Learn

Import the receiver decorator from django.dispatch

Import the post_save signal from django.db.models.signals

Import the User model from django.contrib.auth.models

Create a function that receives the post_save signal for User

Use the @receiver decorator to connect the function to the signal

💡 Why This Matters

🌍 Real World

Automatically running code when users register helps automate tasks like sending welcome messages or setting up profiles.

💼 Career

Understanding Django signals and the receiver decorator is important for backend developers working with Django to handle events cleanly and efficiently.

1

Set up imports and initial function

Write the import statements to bring in receiver from django.dispatch, post_save from django.db.models.signals, and User from django.contrib.auth.models. Then, define an empty function called welcome_new_user that takes sender, instance, created, and **kwargs as parameters.

Django

# Import receiver, post_save, and User
# Define function welcome_new_user(sender, instance, created, **kwargs):
# Your code here

Need a hint?

Remember to import exactly receiver, post_save, and User. Define the function with the exact name and parameters.

2

Add the receiver decorator

Use the @receiver decorator to connect the welcome_new_user function to the post_save signal for the User model.

Django

from django.dispatch import receiver
from django.db.models.signals import post_save
from django.contrib.auth.models import User

# Add the receiver decorator here
@receiver(post_save, sender=User)
def welcome_new_user(sender, instance, created, **kwargs):
    pass

Need a hint?

Use @receiver(post_save, sender=User) exactly above the function definition.

3

Add logic to check if user was created

Inside the welcome_new_user function, add an if statement that checks if created is True. This means the user was just created.

Django

from django.dispatch import receiver
from django.db.models.signals import post_save
from django.contrib.auth.models import User

@receiver(post_save, sender=User)
def welcome_new_user(sender, instance, created, **kwargs):
    # Check if created is True
    if created:
        pass

Need a hint?

Use if created: to check if the user was newly created.

4

Print a welcome message for new users

Inside the if created: block, add a print statement that outputs "Welcome, " followed by the user's username from instance.username.

Django

from django.dispatch import receiver
from django.db.models.signals import post_save
from django.contrib.auth.models import User

@receiver(post_save, sender=User)
def welcome_new_user(sender, instance, created, **kwargs):
    if created:
        # Print welcome message with instance.username
        pass

Need a hint?

Use an f-string to include instance.username in the printed message.