Django Simple History - History Diffing - django

Question

So I'm using django-simple-history for one of my projects. I'm using it on one of the models called "Address" to show the history of the records.
I've created a DetailView to show the information about the address and added context['history'] to show changes of the record. This works all fine.
I would be interested in what field changed, and I read the following; History Diffing
So I somehow need to loop through all the fields from the last two records and find the field which has changed...
I couldn't find any examples on how to achieve this so I tried adding the context to the view
#views.py
class Address(DetailView):
'''
Show details about the address
'''
model = Address
'''
Add history context to the view and show latest changed field
'''
def get_context_data(self, **kwargs):
context = super(Address, self).get_context_data(**kwargs)
qry = Address.history.filter(id=self.kwargs['pk'])
new_record = qry.first()
old_record = qry.first().prev_record
context['history'] = qry
context['history_delta'] = new_record.diff_against(old_record)
return context
And a simple model
#models.py
class Address(models.Model)
name = models.CharField(max_length=200)
street = models.CharField(max_length=200)
street_number = models.CharField(max_length=4)
city = models.CharField(max_length=200)
Template
#address_detail.html
<table>
<thead>
<tr>
<th scope="col">Timestamp</th>
<th scope="col">Note</th>
<th scope="col">Edited by</th>
</tr>
</thead>
<tbody>
{% for history in history %}
<tr>
<td>{{ history.history_date }}</td>
<td>{{ history.history_type }}</td>
<td>{{ history.history_user.first_name }}</td>
</tr>
{% endfor %}
</tbody>
</table>
Somehow this doesn't feel right, there should be a way to iterate over the changes and only add the changed fields to the context...
Any ideas would be appreciated!

Answer 1

I have recently worked on this. I think you are missing a trick you have changes stored in history_delta. You can use this to show the changed fields.
Following will display tabulated result like which field was changed and what was the old and the new value of that field.
{% if history_delta %}
<h3>Following changes occurred:</h3>
<table>
<tr>
<th>Field</th>
<th>New</th>
<th>Old</th>
</tr>
{% for change in delta.changes %}
<tr>
<td>
<b>{{ change.field }}</b>
</td>
<td>
<b>{{ change.new }}</b>
</td>
<td>
<b>{{ change.old }}</b>
</td>
</tr>
{% endfor %}
</table>
{% else %}
<p>No recent changes found.</p>
{% endif %}