how to use initiate function for a cart in Django? - django-models

Question

I'm learning Django and I'm trying to make a Cart, which the customer can get and item and add it in his/her order row and then the order will be submitted. so my teacher said use def initiate(customer), and I don't understand how to use it. Can someone please explain it to me? Thank you.
here is the code I'm working on it:
User = get_user_model()
class Customer(models.Model):
user = models.OneToOneField(User, on_delete=Product, related_name="User")
phone = models.CharField(max_length=20)
address = models.TextField()
balance = models.IntegerField(default=20000)
def deposit(self, amount):
self.balance += amount
self.save()
def spend(self, amount):
if amount > self.balance:
raise ValueError
self.balance -= amount
self.save()
class OrderRow(models.Model):
product = models.ManyToManyField(Product)
order = models.ForeignKey('Order', on_delete=models.CASCADE)
amount = models.IntegerField()
class Order(models.Model):
# Status values. DO NOT EDIT
STATUS_SHOPPING = 1
STATUS_SUBMITTED = 2
STATUS_CANCELED = 3
STATUS_SENT = 4
customer = models.ForeignKey('Customer', on_delete=models.SET_NULL)
order_time = models.DateTimeField(auto_now=True)
total_price = Sum(F('amount') * F('product__price'))
status = models.IntegerField(choices=status_choices)
#staticmethod
def initiate(customer):
Order.initiate(User)
def add_product(self, product, amount):
Order.status = 1
OrderRow.product = Product.objects.get(id=product.id)
print(product.id)
if OrderRow.objects.filter(product=product).exists():
preexisting_order = OrderRow.objects.get(product=product, order=self)
preexisting_order.amount += 1
preexisting_order.save()
else:
new_order = OrderRow.objects.create(
product=product,
cart=self,
amount=1,
)
new_order.save()

Answer 1

You are probably supposed to create a new Order associated with this customer. Something along the following lines:
#classmethod
def initiate(cls, customer):
return cls.objects.create(customer=customer, status=cls.STATUS_SHOPPING)
There are some other issues with your code. You cannot use SET_NULL if the fk is not nullable:
customer = models.ForeignKey('Customer', on_delete=models.SET_NULL, null=true)
There should not be multiple products per row:
class OrderRow(models.Model):
product = models.ForeignKey(Product) # not many2many!
# ...
Also, your add_product needs quite some fixing:
def add_product(self, product, amount):
self.status = self.STATUS_SHOPPING # the instance is self + use your descriptive variables
print(product.id)
# filter only rows in the current order!
if self.orderrow_set.filter(product=product).exists():
# fix naming: this is a row, not an order
preexisting_order_row = self.orderrow_set.get(product=product)
preexisting_order_row.amount += amount # why +1, you are adding amount
preexisting_order_row.save()
else:
new_order_row = OrderRow.objects.create(
product=product,
order=self,
amount=amount,
) # create saves already