Django: Getting last value by date from related model in html-CodePudding

I Just had a question:

So on my parent product overview I show the name of the product and it's URL but there is also a related model to that parent model which holds the history of the prices over time.

What I want to do is show also the latest price in my table here is my code:

models.py:

class Product(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    name = models.CharField(max_length=100, default=None, null=True, blank=True)
    url = models.CharField(max_length=255, default=None, null=True, blank=True)
    creation_date = models.DateTimeField(auto_now_add = True)
    update_date = models.DateTimeField(auto_now = True)


class PriceHistory(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    product_info  = models.ForeignKey(Product, on_delete=models.CASCADE)
    price = models.DecimalField(max_digits=20, decimal_places=2)    
    creation_date = models.DateTimeField(auto_now_add = True)

My views.py

@login_required
def overview(request):
    all_products = Products.objects.filter(user=request.user)
    general_context = {'all_products': all_products}
    return render(request, 'overview.html', general_context)

and my html

    <h4>Overview Products</h4>
        <table>
          <thead>
            <tr>
              <th>#</th>
              <th>Name</th>
              <th>Url</th>
              <th>Last price</th>
            </tr>
          </thead>
          <tbody>
            {% for product in all_products %}   
                <tr>                    
                <td>{{ forloop.counter }}</td>
                <td>{{ product.name }}</td>
                <td>{{ product.url }}</td>
                <td>{{ product.id.price}}</td>
                <td></td>
                {% endfor %}
              </tr>
          </tbody>
        </table>

How to get the latest price also together with my product in my html overview?

I tried with {{ product.id.price}}. I think I'm not far off but can't get my head around it.

CodePudding user response：

You can get the most recent price history using the reverse accessor, ordering by the creation date and then selecting the first object in the queryset:

latest_price_history = product.pricehistory_set.order_by('-creation_date').first()

As to how you get this into your template, you could add this as a model method like so:

class Product(models.Model):
   ...

   @property
   def latest_price(self):
      return self.pricehistory_set.order_by('-creation_date').first().price

Then in your template you can call it by:

{{ product.latest_price }}