Django templates are not showing values of annotations

问题

I would like to display price SUM of all products related to particular room.

Model:

class Item(models.Model):
    product = models.CharField(max_length=150)
    quantity = models.DecimalField(max_digits=8, decimal_places=3)
    price = models.DecimalField(max_digits=7, decimal_places=2)
    purchase_date = models.DateField(null=True, blank=True)
    warranty = models.DecimalField(max_digits=4, decimal_places=1)
    comment = models.TextField()
    room = models.ForeignKey(RoomList)
    user = models.ForeignKey(User)

class RoomList(models.Model):
    room_name =models.CharField(max_length=150)
    user = models.ForeignKey(User)
    size = models.DecimalField(max_digits=5, decimal_places=2)
    comment = models.TextField()

Base on https://docs.djangoproject.com/en/1.6/topics/db/aggregation/#following-relationships-backwards

I created Views:

def items(request):
    total_price = RoomList.objects.annotate(Sum('item__price'))
    return render(request, 'items.html', {'items': Item.objects.filter(user=request.user), 
        'rooms': RoomList.objects.filter(user=request.user), 'total_price': total_price})

Later i pushed this to templates:

<table class="table table-hover">
    <thead>
        <tr>
            <th>Room name</th>
            <th>Costs</th>
        </tr>
    </thead>
    <tbody>
        {% for roomlist in rooms %}
        <tr>
            <td>{{ roomlist.room_name }}</td>
            <td>{{ roomlist.total_price.item__price__sum }}</td>
        </tr>
        {% endfor %}
    </tbody>
</table>

Unfortunately sums are not visible on the page. There is no error. What i did wrong?

回答1:

your view:

def items(request):
    rooms = RoomList.objects.filter(user=request.user).annotate(total_price=Sum('item__price')) # You can filter objects and next add annotates. `annotate(total_price=Sum('item__price')` will add `total_price` to objects.

    return render(request, 'items.html', {'items': Item.objects.filter(user=request.user), 'rooms': rooms) # Returns filtered objects with added annotates.

and template:

<table class="table table-hover">
    <thead>
        <tr>
            <th>Room name</th>
            <th>Costs</th>
        </tr>
    </thead>
    <tbody>
        {% for roomlist in rooms %}
        <tr>
            <td>{{ roomlist.room_name }}</td>
            <td>{{ roomlist.total_price }}</td> {# Your added annotates #}
        </tr>
        {% endfor %}
    </tbody>
</table>

来源：https://stackoverflow.com/questions/24341606/django-templates-are-not-showing-values-of-annotations

标签

django

templates

aggregate

annotate