GhalyahFA / TASK-Django-M13-Signals

I haven't had my coffee yet :(

Setup

1. Fork and clone this repository.
2. Install the requirements using pip install -r requirements/dev.lock.

Signals Setup

1. Create a signals.py file inside of coffeeshops.

2. Go to coffeeshops/apps.py and add a ready method to CoffeeshopsConfig as follows:

   class CoffeeshopsConfig(AppConfig):
       default_auto_field = "django.db.models.BigAutoField"
       name = "coffeeshops"
   
       def ready(self) -> None:
           import coffeeshops.signals

   • This will allow our signals to work when the app starts. You can read about this method here.

Emails

We want to be notified every time a new cafe owner joins our platform. To do that, we need to send an email each time a CafeOwner has been created.

1. Go to coffeeshops/signals.py and import send_mail from django.core.mail (we will need this function later).

2. Create a function called send_new_owner_email, which takes in a sender, instance, created, and **kwargs.

   • Use the send_mail function (read about it here) if created is True.
   • Send an email with the subject as New Cafe Owner and the body of the email as A new cafe owner has joined named <FULL_NAME_OF_CAFE_OWNER>. For the from_email you can use "[e-mail]" and recipient_list can be ["[e-mail]"].

3. Decorate your send_new_owner_email with register, which is imported from django.dispatch (read about decorators here).

4. Add post_save (imported from django.db.models.signals) to your register decorator as the first argument and set the sender parameter equal to CafeOwner (imported from coffeeshops.models).

   • Read about the post_save signal here.

5. Test out your signal by creating an admin account (using ./manage.py createsuperuser), starting the server, logging in to the admin site, and creating a new CafeOwner.

   • You should see a new login TASK-Django-M13-Signals/emails/TIMESTAMP.log (where timestamp is hyphenated numbers) that should look like the following:

     Content-Type: text/plain; charset="utf-8"
     MIME-Version: 1.0
     Content-Transfer-Encoding: 7bit
     Subject: New Cafe Owner
     From: [e-mail]
     To: [e-mail]
     Date: Sat, 23 Jul 2022 22:26:35 -0000
     Message-ID: <165861519536.9692.1816094537173382016@YOUR_COMPUTER_USERNAME>
     
     A new cafe owner has joined named Guido van Rossum.
     -------------------------------------------------------------------------------
     

Slugging

Slug is a newspaper term and a short label for something. It contains only letters, numbers, underscores, or hyphens. They’re generally used in URLs. We want to auto-generate slugs for our CoffeeShop instances.

1. Create a function called slugify_coffee_shop in coffeeshops/signals.py and decorate it with a pre_save signal that has CoffeeShop as its sender (read about pre_save signals here).
2. Check if instance does not have a slug.
3. If our instance does not have a slug then just set instance.slug equal to create_slug(instance) where create_slug is imported from utils (i.e., from utils import create_slug).
4. Test out your signal on the admin site, by creating a new CoffeeShop, you should see a slug assigned to your CoffeeShop after saving.

BONUS: if you can tell an instructor why a pre_save signal must be used for our slugify_coffee_shop receiver and not a post_save signal, you get extra points.

Address Manager

We want to make sure that an address object always exists for a CoffeeShop even if one was never created or if it is deleted.

Create a Default Address

1. Create a function called add_default_address in coffeeshops/signals.py and decorate it with a post_save signal that has CoffeeShop as its sender.
2. Check if the instance has been created, and if instance.location is empty.
   1. Create a CoffeeShopAddress object.
   2. Set instance.location equal to the new CoffeeShopAddress object you've created.
   3. Save your instance.
3. Test out your signal on the admin site by creating a new CoffeeShop and leaving the location field empty, you should see a default location assigned to your CoffeeShop after saving.

Restore a Default Address

1. Create a function called restore_default_address and decorate it with a post_delete signal that has CoffeeShopAddress as its sender (read about post_delete signals here).
2. Get the coffee shop from the deleted instance (hint: use the related name coffee_shop) and store it in a variable called coffee_shop.
3. Create a new CoffeeShopAddress instance.
4. Set coffee_shop.location equal to the new CoffeeShopAddress object you've created.
5. Save your coffee_shop instance.
6. Test out your signal on the admin site, by deleting a location from any CoffeeShop, you should see a default location assigned to the CoffeeShop.

BONUS: if you can tell an instructor why a post_delete signal must be used for our restore_default_address receiver and not a pre_delete signal, you get extra points.

Inventory Management

We want to manage our Drink inventory and mark is_out_of_stock if our drinks go out of stock.

1. Create a function called slugify_coffee_shop in coffeeshops/signals.py and decorate it with a pre_save signal that has Drink as its sender.
2. Set instance.is_out_of_stock to False if instance.stock_count is greater than zero and vice-versa.
3. Test out your signal on the admin site, by setting a stock count greater than zero to a drink, you should see is_out_of_stock as False after saving.