get_object_or_404.py

#clean architecture layers
# https://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html
# ^^you can read read here the beneficts of use this patterns to write better code

# The dependency rule (->): dependencies can only point inwards 
# Infrastructure -> Application -> Domain
# Summary: my business logic (domain) don't know infra or apliccation layers

# Use case summary
# Given a slug 
# I search a Product Entity by slug
# If not exists I will send a 404 response
# If exists I generate a template with product
# I reponse with http page


#I added (I infra) (A Application) (D Domain) to know how acts
def product_detail(request, slug):
    try:
        product = Product.objects.get(slug=slug) # (I Framework, Repository, Database) (D business logic)
    except Product.DoesNotExist: # (D bussines logic)
        raise Http404() # (A presentation layer) (I framework, message bus)
    return TemplateResponse(request, 'products/product_detail.html', { # (I UI) (A presenters)
        'product': product,
    })
  
# Shorter version
def product_detail(request, slug):
  return TemplateResponse(request, 'products/product_detail.html', { # (I) (A)
      'product': get_object_or_404(Product.objects.all(), slug=slug), # (D) (I) (A)
  })

# As you see you are very couple to infra and application layers
# if something in your use case will change tomorrow, you need to rewrite all
# On the other hand, if one layer will changes (database, framework, business logic, json response)
# it will not affect others layers and you have a scalable code and also scalable projects