How to get a value from related object in a django template - django

Question

I'm quite new with python and django and I apologize if the topic was already covered, but I coudln't find an answer to my question.
I have theese classes in my models.py
class Category(models.Model):
category_type = models.CharField(max_length=50)
description = models.TextField()
def __unicode__(self):
return self.category_type
class Area(models.Model):
area_type = models.CharField(max_length=50)
description = models.TextField()
def __unicode__(self):
return self.area_type
class Topic(models.Model):
topic_type = models.CharField(max_length=50)
description = models.TextField()
def __unicode__(self):
return self.topic_type
class Tag(models.Model):
tag_type = models.CharField(max_length=50)
description = models.TextField()
def __unicode__(self):
return self.tag_type
class GenericRecord(models.Model):
document_title = models.CharField(max_length=500)
category = models.ForeignKey("Category")
area = models.ForeignKey("Area")
topic = models.ForeignKey("Topic")
tag = models.ForeignKey("Tag")
note = models.TextField(null=True, blank=True)
link = models.TextField(null=True, blank=True)
file_upload = models.FileField(upload_to='GenericRecord/', null=True, blank=True)
class Meta:
abstract = True
class Document(GenericRecord):
code = models.CharField(max_length=500, null=True, blank=True)
reference = models.CharField(max_length=500)
issue_date = models.DateField(auto_now=False, auto_now_add=False)
validation_date = models.DateField(auto_now=False, auto_now_add=False, null=True, blank=True)
def get_admin_url(self):
return reverse("admin:%s_%s_change" % (self._meta.app_label, self._meta.model_name), args=(self.id,))
def __unicode__(self):
if self.code:
return "%s-%s" % (self.code, self.document_title)
else:
return "--%s" % self.document_title
And this piece of code in views.py
def documents_list(request):
# Generate counts of some of the main objects
num_docs=Document.objects.all().count()
docs=Document.objects.all()
num_articles=Article.objects.all().count()
articles=Article.objects.all()
template='documents_management.html'
for object in docs:
object.fields = dict((field.name, field.value_to_string(object)) for field in object._meta.fields)
# Render the HTML template documents_management.html with the data in the context variable
return render(request,template, context={'docs':docs, 'num_docs':num_docs,'docs':docs, 'num_articles':num_articles, 'articles':articles})
In the template I'm trying to get a table with all the values, but for the related objects I get the primary key (of course).
Here is the code in my template:
<table class="w3-table-all">
{% for object in docs %}
{%if forloop.first %}
<tr>
{% for field, value in object.fields.iteritems %}
<th>{{ field }}</th>
{% endfor %}
</tr>
{%endif%}
{% endfor %}
{% for object in docs %}
{% for field, value in object.fields.iteritems %}
<td>{{ value }}</td>
{% endfor %}
</tr>
{% endfor %}
</table>
What I see in my browser
My question is, how can I get the object Category, Area etc... in order to get the category_type, area_type etc. value?
Thanks!

Answer 1

Here is an great example from the docs: https://docs.djangoproject.com/en/1.11/intro/tutorial03/#use-the-template-system
What you are searching for is the question.choice_set.all part.
UPDATE due to a hint of bad style
As mentioned by daniel you should ditch the Field.to_value_string method.
Since I am not a fan of implicit code I always recommend to code templates as explicit as possible, here would by my version of your template
<table class="w3-table-all">
{% for doc in docs %}
{% if forloop.first %}
<tr>
<th>Document Title</th>
<th>Category Type</th>
<th>Area Type</th>
<th>...</th>
</tr>
{% else %}
<tr>
<td>{{ doc.document_title }}</td>
<td>{{ doc.category.category_type }}</td>
<td>{{ doc.area.area_type }}</td>
<td>...</td>
</tr>
{% endif %}
{% endfor %}
</table>
What I changed:
only one for loop, you started with the if forloop.first you might also finish with the else case
refactored object to doc because objects is used often within django for model managers
add the fields explicit doc.area.area_type, this will prevent a new field in the model to also appear in the template but here I recommend an explicit over an implicit coding style
Also you can remove this from document_list:
for object in docs:
object.fields = dict((field.name, field.value_to_string(object)) for field in object._meta.fields)

Answer 2

The problem is in your use of Field.value_to_string. As the docstring on that method shows, this is for serialization, not for displaying values.
A much simpler and more effective way of doing this would be to use getattr, which gets the actual value; the template will then take care of converting those to a string, which in the case of the foreign keys will call the __unicode__ method of the related objects.
object.fields = dict((field.name, getattr(obj, field.name)) for field in object._meta.fields)