问Django购物车不更新数量

EN

{% block content %}
<h1>Cart Page Here</h1>
Cart item count: {{cart_item_count }}
{% endblock %}

# Create your views here.
from django.shortcuts import render_to_response
from django.template import RequestContext
from cart import carts as cart

def show_cart(request, template_name="cart/cart.html"):
    cart_item_count = cart.cart_disinct_item_count(request)
    page_title = 'Shopping Cart'
    return render_to_response("cart/cart.html", locals(),
                          context_instance = RequestContext(request))

class CartItem(models.Model):
cart_id = models.CharField(max_length=50)
date_added = models.DateTimeField(auto_now_add = True)
quantity = models.IntegerField(default = 1)
product = models.ForeignKey('catalog.Product', unique = False)

class Meta:
    app_label = ''
    db_table = 'cart_items'
    ordering = ['date_added']

def total(self):
    return self.quantity * self.product.price
def name(self):
    return self.product.name
def price(self):
    return self.product.price

def get_absolute_url(self):
    return self.product.get_absolute_url()
def augment_quantity(self, quantity):
        """ called when a POST request comes in for a Product instance already in the shopping cart """
        self.quantity = self.quantity + int(quantity)
        self.save()

def get_cart_items(request):
    return CartItem.objects.filter(cart_id=_cart_id(request))

#add an item to the cart
def add_to_cart(request):    
    postdata = request.POST.copy()
    #get product slug from post data, return blank if empty
    product_slug = postdata.get('product_slug', '')
    #get quantity added, return 1 if empty
    quantity = postdata.get('quantity', 1)
    #fetch the product or return a missing page error
    p = get_object_or_404(Product, slug = product_slug)
    #get products in cart
    cart_products = get_cart_items(request)
    product_in_cart = False
    #check to see if item is already in cart
    for cart_item in cart_products:
        if cart_item.product.id == p.id:
            #update the quantity if found
            cart_item.augment_quantity(quantity)
            product_in_cart = True
        if not product_in_cart:
            #create and save a new cart item
            ci = CartItem()
            ci.product = p
            ci.quantity = quantity
            ci.cart_id = _cart_id(request)
            ci.save()
#returns the total number of items in the user's cart
def cart_disinct_item_count(request):
    return get_cart_items(request).count()

class ProductAddToCartForm(forms.Form):
quantity = forms.IntegerField(widget=forms.TextInput(attrs={'size':'2',
                              'value':'1', 'class':'quantity'}),
                              error_messages={'invalid': 'Please enter a valid quantity'},
                              min_value = 1)
product_slug = forms.CharField(widget = forms.HiddenInput())

#override the default __init__ so we can set the request
def __init__(self, request = None, *args, **kwargs):
    self.request = request
    super(ProductAddToCartForm, self).__init__(*args, **kwargs)

#new product view, with POST vs GET detection

p = get_object_or_404(Product, slug=product_slug)

categories = p.categories.all()
page_title = p.name
meta_keywords = p.meta_keywords
meta_description = p.meta_description
#need to evaluate the HTTP method
if request.method == 'POST':

    #add to cart....create the bound form
    postdata = request.POST.copy()
    form = ProductAddToCartForm(request, postdata)

    #check if posted data is valid
    if form.is_valid():
        #add to cart and redirect to cart page
        cart.add_to_cart(request)
        # if test cookie worked, get rid of it
        if request.session.test_cookie_worked():
            request.session.delete_test_cookie()

        url = urlresolvers.reverse('show_cart')
        return HttpResponseRedirect(url)
else:
    # it's a GET, create the unbound form. Note request as a kwarg
    form = ProductAddToCartForm(request = request, label_suffix = ':')


    #assign the hidden input the product slug
    form.fields['product_slug'].widget.attrs['value'] = product_slug
    #set the test cookie on our first GET request
    request.session.set_test_cookie()

    return render_to_response("catalog/product.html", locals(),   context_instance=RequestContext(request))