lnysrogh wrote:
> Hello. I'm new to Django (and web development in general), and this is
> my first post here. Hope someone can help me.
>
> I'm trying to build a shopping cart, and my idea is to store the
> product information (id and quantity) in a session when I add the
> product to the shopping cart, and retrieve it to display in the "show
> cart" page. I'm using sessions for this because I don't want the user
> to have to log in or register just to add some items to the cart and
> see the total price. When he logs in to actually buy something, I
> pretend to store it in a cart model, but I didn't get there yet. I'll
> show you the code I'm testing:
>
> def add(request, product_id):
> request.session.set_test_cookie()
> if request.session.test_cookie_worked():
> request.session.delete_test_cookie()
> added = Product.objects.get(id=product_id)
> request.session['product_id'] = added
> return HttpResponseRedirect('/cart/')
> else:
> return HttpResponse('You need to enable cookies')
>
> def cart(request):
> if 'product_id' in request.session:
> cart = request.session['product_id']
> return render_to_response('cart.html', {'cart': cart})
> else:
> return HttpResponse('Cart is empty')
>
> That's what I was able to come up with. The first problem is, it's not
> working. The second problem is, I can't figure out how to add more
> than one product to the cart.
>
> The error I'm getting when I add something to the cart is "Caught an
> exception while rendering: 'Product' object is not iterable". I'm
> pretty sure that error has something to do with the cart.html, because
> if I replace that line with:
>
> return HttpResponse('You've added the product %s to the cart' % cart)
>
> it works. The cart.html is just this:
>
> {% for product in cart %}
> <p>Your cart: {{ product.name }} - {{product.price}}</p>
> {% endfor %}
>
> It should work, right? I just can't figure what's causing that error.
>
I've noticed a few things that you should consider:
Firstly, you're storing the actual product object in the session which
is less than ideal, it'd be better to load any cart objects from the db
at the start of each request. This prevents the problem of a session
product and the real db product getting out of sync if a change is made.
Second problem is that you're assigning request['product_id'] to an
actual product, but when you're doing the lookup later you're treating
it as if it is a list of products. When you think about it, it's clear
why iterating over it isn't working.
What I would do is have a Cart model which contains a set of Products (I
tend to create a CartItem model as well for storing other info such as
quantity). Normally you'd just save this to the db and store the cart id
in the session. This can create a problem with having a bunch of orphan
carts in the db after the sessions have expired though, normal solution
is to have a script that periodically cleans up any old carts. Other
solution is that you store the Cart model in the session but make sure
the serialized CartItem only stores the product id rather than the whole
product.
Hope this helps
Regards,
Andrew Ingram
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