I'm trying to sort related items in a template by a field in a model three ForeignKey relationships away. I'm assembling the data for the template in the view as proposed in another StackOverflow answer:
Sorting related items in a Django template
As far as I can tell, I copied the code from this as-is except for I had to change variable names. It doesn't throw an error, it just displays no list items in the HTML unordered list.
# checkout.html
{% for item in cart_items %}
<tr>
<td class="left">
{{ item.name }}
<ul>
{% for part in part_list %}
<li>{{ part.name }}
{% endfor %}
</ul></td>
</tr>
{% endfor %}
And the view...
# views.py
def checkout(request):
cart_items = get_cart_items(request)
itemCollection = []
for item in cart_items:
item.part_list = item.product.buildpart.all().order_by('product__family__type')
itemCollection.append(item)
return render(request, 'checkout.html', locals())
And the get_cart_items function:
# cart.py
def get_cart_items(request):
""" return all items from the current user's cart """
return CartItem.objects.filter(cart_id=get_cart_id(request))
As I said, the template and view are pretty much copies of the solution presented in the aforementioned StackOverflow article. One thing I thought was curious was that itemCollection[] from the view is never referenced in the template.
I believe the order_by clause ('product__family__type') is right only because it doesn't generate an error. But in case that is the problem or a part of it here is the chain of models I am attempting to navigate in that order_by clause:
We start from the shopping cart model (CartItem):
class Item(models.Model):
cart_id = models.CharField(max_length=50)
quantity = models.IntegerField(default=1)
product = models.ForeignKey(PartModel, unique=False)
class Meta:
abstract = True
class CartItem(Item):
date_added = models.DateTimeField(auto_now_add=True)
class Meta:
ordering = ['date_added']
verbose_name = "Cart Item"
Through the 'product' field we get to the model holding our inventory and its self-referential BuildPart ManyToMany model:
class PartModel(models.Model):
family = models.ForeignKey(PartFamily)
name = models.CharField("Model Name", max_length=50, unique=True)
buildpart = models.ManyToManyField('self', through='BuildPart',
symmetrical=False, related_name='+')
class Build(models.Model):
build = models.ForeignKey(PartModel, related_name='+')
part = models.ForeignKey(PartModel, related_name='+')
quantity = models.PositiveSmallIntegerField(default=1)
class Meta:
abstract = True
unique_together = ('build', 'part')
def __unicode__(self):
return self.build.name + ' with ' + str(self.quantity) + ' * ' + \
self.part.family.make.name + ' ' + self.part.name
class BuildPart(Build):
pass
class Meta:
verbose_name = "Build Part"
From there we follow the 'family' field to the PartFamily model:
class PartFamily(models.Model):
make = models.ForeignKey(PartMake)
type = models.ForeignKey(PartType)
name = models.CharField("Family Name", max_length=30,
unique=True)
slug = models.SlugField(unique=True)
And lastly, we get to the model with the 'order' field, the one we wish to sort the related items by, PartType:
class PartType(models.Model):
name = models.CharField("Part Type", max_length=30, unique=True)
slug = models.SlugField(unique=True)
order = models.PositiveSmallIntegerField()
description = models.TextField(blank=True, null=True)
To recap, how do I get the shopping cart products' related items, and sort them by the 'order' field in the PartType model?
