Using multiple models for django ecommerce cart - django

Question

I'm making a cart for an ecommerce project that I am working on, at the moment the cart does work. However it only works for one model and I'm not sure how to make it work with more than one.
This is my contexts.py file in my cart folder:
from django.shortcuts import get_object_or_404
from courses.models import Course
from food_order.models import Food_order
def cart_contents(request):
"""
Ensures that the cart contents are available when rendering
every page
"""
cart = request.session.get('cart', {})
cart_items = []
total = 0
course_count = 0
for id, quantity in cart.items():
course = get_object_or_404(Course, pk=id)
total += quantity * course.price
course_count += quantity
cart_items.append({'id': id, 'quantity': quantity, 'course': course})
return {'cart_items': cart_items, 'total': total, 'course_count': course_count}
Here is my views.py
from django.shortcuts import render, redirect, reverse
# Create your views here.
def view_cart(request):
"""A View that renders the cart contents page"""
return render(request, "cart.html")
def add_to_cart(request, id):
"""Add a quantity of the specified product to the cart"""
quantity = int(request.POST.get('quantity'))
cart = request.session.get('cart', {})
if id in cart:
cart[id] = int(cart[id]) + quantity
else:
cart[id] = cart.get(id, quantity)
request.session['cart'] = cart
return redirect(reverse('index'))
def adjust_cart(request, id):
"""
Adjust the quantity of the specified product to the specified
amount
"""
quantity = int(request.POST.get('quantity'))
cart = request.session.get('cart', {})
if quantity > 0:
cart[id] = quantity
else:
cart.pop(id)
request.session['cart'] = cart
return redirect(reverse('view_cart'))
So I have 2 different classes I would like to be able to add to the cart from 2 different places on the ecommerce site. I am just uncertain how to acheive this.
If I do something along the lines of:
from django.shortcuts import get_object_or_404
from courses.models import Course
from food_order.models import Food_order
def cart_contents(request):
"""
Ensures that the cart contents are available when rendering
every page
"""
cart = request.session.get('cart', {})
cart_items = []
total_food_order = 0
total_course = 0
total = 0
product_count = 0
for id, quantity in cart.items():
course = get_object_or_404(Course, pk=id)
food_order = get_object_or_404(Food_order, pk=id)
total_course += quantity * course.price
total_food_order += quantity * food_order.price
product_count += quantity
cart_items.append({'id': id, 'quantity': quantity, 'course': course, 'food_order':food_order})
total = total_course + total_food_order
return {'cart_items': cart_items, 'total': total, 'product_count': product_count}
Then the resulting cart_items will be:
[{'id': '1', 'quantity': 1, 'course': <Course: Basic Order Taking>, 'food_order': <Food_order: Onions>}, {'id': '2', 'quantity': 3, 'course': <Course: Advanced Order Taking>, 'food_order': <Food_order: Peppers>}]
I understand why it's doing this, but I cannot think of a way to adjust my code to get the desired result. Any pointers would be very appreciated.
Thank you for your time.

Answer 1

I would suggest making an base model for all your models that need to be added to the cart, and use multi-table inheritence.
class BaseCartItem(models.Model):
price = models.DecimalField()
item_type = models.CharField(max_length=20, editable_false)
....
def save(*args, **kwargs):
self.item_type = self._get_item_type()
return super().save(*args, **kwargs)
def _get_item_type(self):
raise NotImplementedError
class Course(BaseCartItem):
....
def _get_item_type(self):
return "Course"
class FoodOrder(BaseCartItem):
....
def _get_item_type(self):
return "Food Order"
# if you want to add to the db
class Cart(models.Model)
item = models.ForeignKey(BaseCartItem, on_delete=models.CASCADE)
quantity = models.PositiveIntegerField()
....
And in the views everything remains the same. You just use the ids of the base model rather than the child models.
The cart_contents is simplified a bit
def cart_contents(request):
"""
Ensures that the cart contents are available when rendering
every page
"""
cart = request.session.get('cart', {})
cart_items = []
item_groups = defaultdict(int)
total = 0
product_count = 0
items_map = {
item.id: item
for item in BaseCartItem.objects.filter(id__in=cart.keys()
}
for id, quantity in cart.items():
item = items_map[id]
item_group[item.item_type] += quantity * item.price
product_count += quantity
cart_items.append({'id': id, 'quantity': quantity, 'course': item, 'food_order':item})
total = sum(item_groups.values())
return {'cart_items': cart_items, 'total': total, 'product_count': product_count}