Missteps in Django - Part 2

My next misstep was related to using the regroup tag that I mentioned in the previous post.

First, let's take a look at the example model I'm working with.

class Shipment(models.Model):
 description = models.TextField()
 created = models.DateTimeField(auto_now_add=True);

I wanted to display these Shipments grouped by they day they had been created and I wanted that day formated like "2008-12-22". Since the 'created' field of the Shipment model is a datetime.datetime instance which, when viewed as a string, looks like "2008-12-23 19:16:06.700114". That was a bit too verbose and besides, I wanted shipments grouped by day, not by microsecond!

My solution was to a add a property (of course!) to my model and see if I could use that in the regroup tag. Here's what that looked like:

class Shipment(models.Model):
    description = models.TextField()
    created = models.DateTimeField(auto_now_add=True);

    def _get_ship_date(self):
        return self.created.date()

    ship_date = property(_get_ship_date)

Then in my regroup tag, I could do this:

<ul>
{% regroup shipments by ship_date as shipments_by_date %}
{% for ship_date in shipments_by_date %}
    <li>Shipments for {{ ship_date.grouper }} </li>
    <ol>
    {% for shipment in ship_date.list %}
        <li> {{ shipment.description }} </li>
    {% endfor %}
    </ol>
{% endfor %}
</ul>

Hey, that worked, but this was another of my newbie missteps because there was an aspect to the regroup tag that I had overlooked (this series should be called RTFM maybe?). You can apply a filter to the attribute you are regrouping on like so:

{% regroup ship_list by created|date:"Y-n-d" as shipments_by_date %}

And you're done.