UpdateView – Class Based Views Django

UpdateView refers to a view (logic) to update a particular instance of a table from the database with some extra details. It is used to update entries in the database, for example, updating an article at geeksforgeeks. We have already discussed basics of Update View in Update View – Function based Views Django. Class-based views provide an alternative way to implement views as Python objects instead of functions. They do not replace function-based views, but have certain differences and advantages when compared to function-based views:

• Organization of code related to specific HTTP methods (GET, POST, etc.) can be addressed by separate methods instead of conditional branching.
• Object oriented techniques such as mixins (multiple inheritance) can be used to factor code into reusable components.

Class based views are simpler and efficient to manage than function-based views. A function based view with tons of lines of code can be converted into a class based views with few lines only. This is where Object Oriented Programming comes into impact.

Django UpdateView – Class Based Views

Illustration of How to create and use UpdateView using an Example. Consider a project named geeksforgeeks having an app named geeks.

Refer to the following articles to check how to create a project and an app in Django.

• How to Create a Basic Project using MVT in Django?
• How to Create an App in Django ?

After you have a project and an app, let’s create a model of which we will be creating instances through our view. In geeks/models.py,

# import the standard Django Model
# from built-in library
from django.db import models

# declare a new model with a name "GeeksModel"
class GeeksModel(models.Model):

    # fields of the model
    title = models.CharField(max_length = 200)
    description = models.TextField()

    # renames the instances of the model
    # with their title name
    def __str__(self):
        return self.title

After creating this model, we need to run two commands in order to create Database for the same.

Python manage.py makemigrations
Python manage.py migrate

Now let’s create some instances of this model using shell, run form bash,

Python manage.py shell

Enter following commands

>>> from geeks.models import GeeksModel
>>> GeeksModel.objects.create(
                       title="title1",
                       description="description1").save()
>>> GeeksModel.objects.create(
                       title="title2",
                       description="description2").save()
>>> GeeksModel.objects.create(
                       title="title2",
                       description="description2").save()

Now we have everything ready for back end. Verify that instances have been created from http://localhost:8000/admin/geeks/geeksmodel/

Class Based Views automatically setup everything from A to Z. One just needs to specify which model to create UpdateView for, then Class based UpdateView will automatically try to find a template in app_name/modelname_form.html. In our case it is geeks/templates/geeks/geeksmodel_form.html. Let’s create our class based view. In geeks/views.py,

# import generic UpdateView
from django.views.generic.edit import UpdateView

# Relative import of GeeksModel
from .models import GeeksModel

class GeeksUpdateView(UpdateView):
    # specify the model you want to use
    model = GeeksModel

    # specify the fields
    fields = [
        "title",
        "description"
    ]

    # can specify success url
    # url to redirect after successfully
    # updating details
    success_url ="/"

Now create a url path to map the view. In geeks/urls.py,

from django.urls import path

# importing views from views..py
from .views import GeeksUpdateView
urlpatterns = [
    # <pk> is identification for id field,
    # <slug> can also be used
    path('<pk>/update', GeeksUpdateView.as_view()),
]

Create a template in templates/geeks/geeksmodel_form.html,

<form method="post">
    {% csrf_token %}
    {{ form.as_p }}
    <input type="submit" value="Save">
</form>

Let’s check what is there on http://localhost:8000/1/update/