Экземпляры модели не отображаются в шаблоне

Заказы и OrderItems успешно добавляются в таблицу, но товары не отображаются в шаблоне. Если я использую print(order_item.objects.all()), то возникает ошибка :

AttributeError: Manager isn't accessible via OrderItem instances.

В базе данных django-admin товары красиво добавляются и удаляются из корзины. В настоящее время это товары моего заказа:

Order item
    3 of Saregama Carvaan Earphones GX01 with Mic
    5 of JBL Flip 5
    3 of Puma Unisex-Adult BMW MMS R-cat Mid Sneaker
    4 of Adidas Men's Astound M Running Shoe

4 order items

Эти позиции заказа получены от пользователя admin.

html:

{% block content %}
  <main>
    <div class="container">

    <div class="table-responsive text-nowrap">
    <h2>Order Summary</h2>
    <table class="table">
        <thead>
        <tr>
            <th scope="col">#</th>
            <th scope="col">Item title</th>
            <th scope="col">Price(₹)</th>
            <th scope="col">Quantity</th>
            <th scope="col">Total Item Price</th>
        </tr>
        </thead>
        <tbody>
        {% for order_item in order.items.all %}
        <tr>
            <th scope="row">{{ forloop.counter }}</th>
            <td>{{ order_item.item.product_title }}</td>
            <td>₹{{ order_item.item.sale_price }}</td>
            <td>
                <a href="{% url 'remove-single-item-from-cart' order_item.item.slug %}"><i class="fas fa-minus mr-2"></i></a>
                {{ order_item.quantity }}
                <a href="{% url 'add-to-cart' order_item.item.slug %}"><i class="fas fa-plus ml-2"></i></a>
            </td>
            <td>
            {% if order_item.item.discount %}
                ₹{{ order_item.get_total_discount_item_price }}
                <span class="badge badge-primary">Saving ₹{{ order_item.get_amount_saved }}</span>
            {% else %}
                ₹{{ order_item.get_total_item_price }}
            {% endif %}
            <a style='color: red;' href="{% url 'remove-from-cart' order_item.item.slug %}">
                <i class="fas fa-trash float-right"></i>
            </a>
            </td>
        </tr>
        {% empty %}
        <tr>
            <td colspan='5'>Your cart is empty</td>
        </tr>
        <tr>
            <td colspan="5">
            <a class='btn btn-primary float-right' href="{% url 'productdetails' %}">Continue shopping</a>
            </td>
        </tr>
        {% endfor %}
         {% if object.get_total %}
        <tr>
            <td colspan="4"><b>Order Total</b></td>
            <td><b>₹{{ object.get_total }}</b></td>
        </tr>
        <tr>
            <td colspan="5">
            <a class='btn btn-warning float-right ml-2' href="">Proceed to checkout</a>
            <a class='btn btn-primary float-right' href="">Continue shopping</a>
            </td>
        </tr>
        {% endif %}
        </tbody>
    </table>

    </div>

    </div>
  </main>

{% endblock content %}

модели:

class OrderItem(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    ordered = models.BooleanField(default=False)
    item = models.ForeignKey(AffProduct, on_delete=models.CASCADE)
    quantity = models.IntegerField(default=1)

    objects = models.Manager()

    def __str__(self):
        return f"{self.quantity} of {self.item.product_title}"

    def get_total_item_price(self):
        return self.quantity * self.item.sale_price

    def get_total_discount_item_price(self):
        return self.quantity * (self.item.discount / Decimal('100'))

    def get_amount_saved(self):
        return self.get_total_item_price() - self.get_total_discount_item_price()

    def get_final_price(self):
        if self.item.discount_price:
            return self.get_total_discount_item_price()
        return self.get_total_item_price()


class Order(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    items = models.ManyToManyField(OrderItem)
    start_date = models.DateTimeField(auto_now_add=True)
    ordered_date = models.DateTimeField()
    ordered = models.BooleanField(default=False)

    objects = models.Manager()

    def __str__(self):
        return self.user.username

    def get_total(self):
        total = 0
        for order_item in self.items.all():
            total += order_item.get_final_price()
        return total

просмотров:

@login_required
def add_to_cart(request, slug):
    item = get_object_or_404(AffProduct, slug=slug)
    order_item, created = OrderItem.objects.get_or_create(
        item=item,
        user=request.user,
        ordered=False
    )
    order_qs = Order.objects.filter(user=request.user, ordered=False)
    if order_qs.exists():
        order = order_qs[0]
        # check if the order item is in the order
        if order.items.filter(item__slug=item.slug).exists():
            order_item.quantity += 1
            order_item.save()
            messages.info(request, "This item quantity was updated.")
            print(order_item)
            return redirect("cart")
        else:
            order.items.add(order_item)
            messages.info(request, "This item was added to your cart.")
            print(order_item)
            return redirect("cart")
    else:
        ordered_date = timezone.now()
        order = Order.objects.create(
            user=request.user, ordered_date=ordered_date)
        order.items.add(order_item)
        messages.info(request, "This item was added to your cart.")
        print(order_item)
        return redirect("cart")

@login_required
def add_to_cart(request, slug):
    item = get_object_or_404(AffProduct, slug=slug)
    order_item, created = OrderItem.objects.get_or_create(
        item=item,
        user=request.user,
        ordered=False
    )
    order = Order.objects.filter(user=request.user, ordered=False).first()
    if order:
        # check if the order item is in the order
        if order.items.filter(item__slug=item.slug).exists():
            order_item.quantity += 1
            order_item.save()
            messages.info(request, "This item quantity was updated.")         
        else:
            order.items.add(order_item)
            messages.info(request, "This item was added to your cart.")
    else:
        ordered_date = timezone.now()
        order = Order.objects.create(
            user=request.user, ordered_date=ordered_date)
        order.items.add(order_item)
        messages.info(request, "This item was added to your cart.")
    return render(request, '<template-name>', {'order_item': order_item, 'object': order})