Django/ How get sum of order - 'int' object is not iterable - django

Question

I'm trying to withdraw the order amount using the method from the model, but I can't. Have error - 'int' object is not iterable
models.py
class OrderItem(models.Model):
order = models.ForeignKey(Order, on_delete=models.PROTECT)
product = models.ForeignKey(Product, on_delete=models.PROTECT)
price = models.IntegerField()
quantity = models.PositiveIntegerField(default=1)
def get_total_price(self):
return sum(self.get_price())
def get_price(self):
return self.price * self.quantity
def __str__(self):
return str(self.order)
get_price method it's work, but in get_total_price have error, what I'am doing wrong?
order_success.html
{% for item in order_item %}
<tr>
<td>{{item.quantity}}</td>
<td>{{item.price}}</td>
<td>{{item.get_price}}</td>
</tr>
{% endfor %}
<h2>To pay - {{order_item.get_total_price}}</h2> # doesn't work
can you help me write right the sum method, please. I think my method is wrong.

Answer 1

Can you help me write right the sum method, please. I think my method is wrong.
I think your modeling is wrong. An OrderItem has no total_price, it has a certain price that is the quantity times the unit price, but the total price is an attribute of the entire queryset.
We can however calculate such aggregates, by using a queryset in the view for that, like:
from django.db.models import F, Sum
def some_view(request):
order_items = OrderItems.object.all() # might be a different query
aggrs = order_items.aggregate(
total_price=Sum(F('quantity') * F('price'))
)
context = {
'order_items': order_items,
'aggrs': aggrs
}
return render(request, 'some_template.html', context)
In the template, we can then render it like:
{% for item in order_items %}
<tr>
<td>{{item.quantity}}</td>
<td>{{item.price}}</td>
<td>{{item.get_price}}</td>
</tr>
{% endfor %}
<h2>To pay - {{ aggr.total_price }}</h2>
Note: since your order_item is a collection, it makes more sense to use a plular (like order_items here in this sample view).
Note: it makes sense to define this on the Order model, for example:
class Order(models.Model):
# ...
#property
def total_price():
return self.order_item_set.aggregate(
total_price=Sum(F('quantity') * F('price'))
)['total_price']
then we can thus write some_order.total_price to obtain the total price of that Order object.
Note: it is a bit confusing that you have a price field and a get_price method, perhaps you should consider renaming price to
unit_price, and then make get_price a #property named price.