CODEWITHSUNDEEP
djangodjango-modelsforeign-keysmany-to-one
Davtho1983
Davtho1983

Reputation: 3954

Modeling product orders in Django

I have an order of a certain list of products, and I need to model this in Django.

Each order has properties:

id
email
total_price
line_items

line_items is a dictionary of products and the number of instances of that product required.

Product is a separate model describing a class of products.

I need a many-to-many relationship between Product and Order because each product could be part of many orders, but each order could have many products - how does this look in my fields given that I could have an order that has 3 instances of one product, 2 of another etc...?

Upvotes: 2

Views: 6423

Answers (1)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 477190

line_items is a dictionary of products and the number of instances of that product required.

I would suggest not to store this in a dictionary. In a relational database, one typically stores this in a different table over multiple records. The advantage of this, is that it is easy to query. For example to generate a list of all orders that contain a certain product, or contain a certain product with a quantity higher than 50.

We thus typically have three tables:

+-------+  1    N  +--------------+  N    1  +---------+
| Order |----------| OrderProduct |----------| Product |
+-------+          +--------------+          +---------+
| email |          | quantity     |
+-------+          +--------------+

We thus have three models: Order, OrderProduct and Product, for example:

Order(models.Model):
    email = models.EmailField()

Product(models.Model):
    # ...
    pass

OrderProduct(models.Model):
    order = models.ForeignKey(Order, on_delete=models.CASCADE)
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    quantity = models.IntegerField(default=1)

    class Meta:
        unique_together = ('order', 'product')

We thus can construct an order like:

product1 = Product.objects.create()
product2 = Product.objects.create()
my_order = Order.objects.create(email='[email protected]')
OrderProduct.objects.create(product=product1, order=my_order)
OrderProduct.objects.create(product=product2, order=my_order, quantity=14)

So here we constructed two products and one order, and we added two OrderProducts to this order, one for product1, and one for product2 with a quantity of 14.

Upvotes: 11

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