CODEWITHSUNDEEP
pythondjangomodeldjango-templates
adamF
adamF

Reputation: 1061

Django model object with dynamically added attributes

I'm looking for a way to dynamically add extra attributes to django model instances so that they are accessible in the template

For example,

in models.py

class Foo(models.Model):
    name = models.TextField()

in views.py

def my_view(request):
    f = Foo.objects.get(id=1234)

    # method in question
    f.____add_extra_attribute____('extra_attribute', attr_value)

    return render(request, 'my_template.html', {'foo_instance':f})

in my_template.html

<h1>{{ foo_instance.name }}</h1>
<p>{{ foo_instance.extra_attribute }}</p>

is there a way to accomplish this without rendering the instance as a dictionary instead of a Foo model object?

Upvotes: 4

Views: 9812

Answers (2)

Arindam Roychowdhury
Arindam Roychowdhury

Reputation: 6503

Look at the example below. This is real code from my project. Here I have attached an attribute to the model object itself.

My model:

class Task(models.Model):
    name = models.CharField(max_length=500)
    description = models.TextField(max_length=500, blank=True)
    assignee = models.ForeignKey(Employee, on_delete=models.CASCADE)
    project = models.ForeignKey(Project, on_delete=models.CASCADE, null=True)
    report = models.ForeignKey(UtilizationReport, on_delete=models.CASCADE, null=True)
    role = models.ForeignKey(Role, on_delete=models.CASCADE, null=True, blank=True)
    billable_efforts = models.FloatField(
        validators=[MinValueValidator(0.0), MaxValueValidator(1.0)],
        )
    created_at = models.DateTimeField(default=timezone.now, editable=False)
    reviewed = models.BooleanField(default=False)

In view.py:

task = Task.objects.get(id=1) # Just an example...won't be really using get with id
task_rate = BillingCatagoryRate.objects.get(rate_card=invoice.rate_card, billing_category=task.assignee.billing_category).billing_rate
task.task_price = task_rate * task.billable_efforts # Note: task_price is NOT a model field.

In the template:

<td class="text-center">{{ task.task_price }}</td>

Upvotes: 0

alecxe
alecxe

Reputation: 473813

Following @mgilson's comment, you can pass the extra_attribute to the template in a separate context variable:

def my_view(request):
    f = Foo.objects.get(id=1234)
    extra_attribute = attr_value
    return render(request, 'my_template.html', 
                  {'foo_instance': f, 'extra_attribute': attr_value})

If you still want to set the attribute on a model instance, you can set it directly:

f.extra_attribute = attr_value

Upvotes: 4

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