字段“id”需要一个数字,但得到(字符串)

我正在创建一家有各种颜色的T恤店。在添加到购物车时,我遇到了以下错误: 字段“id”需要一个数字,但得到了“woodstock”。Woodstock是这件衬衫的名字,但我正在将cartid传递给函数。cartid实际上是在remove_from_cart函数中使用的,但是我不确定当我将add推到cart时为什么会抛出错误。 这是购物车模型:

class Cart(models.Model):
    #user = models.ForeignKey(User, null=True, blank=True, on_delete=models.CASCADE)
    total = models.DecimalField(max_digits=100, decimal_places=2, default=0.00)
    timestamp = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)
    active = models.BooleanField(default=True)

    def __str__(self):
        return "Cart id: %s" %(self.id)

class CartItem(models.Model):
    cart = models.ForeignKey(Cart, on_delete=models.CASCADE, null=True, blank=True)
    product = models.ForeignKey(Product,on_delete=models.CASCADE)
    variations = models.ManyToManyField(Variation, blank=True)
    quantity = models.IntegerField(default=1)
    line_total = models.DecimalField(default=10.99, max_digits=100, decimal_places=2)
    timestamp = models.DateTimeField(auto_now_add=True, auto_now=False)
    updated = models.DateTimeField(auto_now=True)

    def __str__(self):
        try:
            return str(self.cart.id)
        except:
            return self.product.name

views.py

def view(request):
    print("viewing cart")
    try:
        the_id = request.session['cart_id']
    except:
        the_id = None
    if the_id:
        cart = Cart.objects.get(id=the_id)
        new_total = 0.00
        for item in cart.cartitem_set.all():
            line_total = float(item.product.price) * item.quantity
            new_total += line_total
        request.session['items_total'] = cart.cartitem_set.count()
        cart.total = new_total
        cart.save()

        context = {"cart":cart}
    else:
        empty_message = "Your cart is empty, please keep shopping"
        context = {"empty": True, "empty_message": empty_message}

    template = "cart/view.html"
    return render(request, template, context)


def add_to_cart(request, slug):
    print("add_to_cart pressed")
    request.session.set_expiry(100000000)
    try:
        the_id = request.session['cart_id']
    except:
        #create cart id
        new_cart = Cart()
        new_cart.save()
        request.session['cart_id'] = new_cart.id
        the_id = new_cart.id
    cart = Cart.objects.get(id=the_id)
    try:
        product = Product.objects.get(slug=slug)
    except Product.DoesNotExist:
        pass
    except:
        pass
    product_variations = []
    if request.method == 'POST':
        qty = request.POST['qty']
        for item in request.POST:
            key = item
            val = request.POST[key]
            try:
                v = Variation.objects.get(product=product, category__iexact=key, title__iexact=val)
                product_variations.append(v)
            except:
                pass
        cart_item = CartItem.objects.create(cart=cart, product=product)
        if len(product_variations) > 0:
            cart_item.variations.add(*product_variations)
        cart_item.quantity = qty
        cart_item.save()
        print("cart item added")


        return HttpResponseRedirect(reverse("carts:cart"))


    return HttpResponseRedirect(reverse("carts:cart"))

def remove_from_cart(request, id):
    print(id) #this is showing the item name, the reason it's not working. Either traced back to html view or urls.py
    try:
        the_id = request.session['cart_id']
        cart = Cart.objects.get(id=the_id)
    except:
        return HttpResponseRedirect(reverse("carts:cart"))
        
    cartitem = CartItem.objects.get(id=id)#error is traced to this line
    cartitem.cart = None
    cartitem.save()
    return HttpResponseRedirect(reverse("carts:cart"))

html

{% block content %}
<div class="col-sm-8 offset-sm-2">
{% if empty %}
  <h1 style="text-align:center;">{{ empty_message }}</h1>
{% else %}

  <table class="table">
    <thead>
      <th>Item</th>
      <th>Price</th>
      <th>Qty</th>
      <th></th>
    </thead>
    <tfoot>
      <tr>
        <td></td>
        <td></td>
        <td>Total: {{ cart.total }}</td>
      </tr>
    </tfoot>
    {% for item in cart.cartitem_set.all %}
    <tr>
      <td>{{ item.product }}
        {% if item.variations.all %}
        <ul>
        {% for var in item.variations.all %}
        <li> {{ var.category|capfirst }} : {{ var.title|capfirst }}</li>
        {% endfor %}
        </ul>
        {% endif %}
      </td>

      <td>{{ item.product.price }}</td>
      <td>{{ item.quantity }}</td>
      <td><a href='{% url "carts:remove_from_cart" item.id %}'>Remove</a></td>
    </tr>
    {% endfor %}
  </table>

{% endif %}
</div>
{% endblock %}

购物车的URL.py

app_name='carts'

urlpatterns =[
    path('cart/', views.view, name='cart'),
    path('cart/<id>/', views.remove_from_cart, name='remove_from_cart'),
    path('cart/<slug:slug>/', views.add_to_cart, name='add_to_cart'),

]

研究这个问题的一个建议是删除迁移并运行makemigrations/migrate,但这对我不起作用。是否有其他建议,或者item.id传递名称而不是id的原因?