ListView – Class Based Views Django

List View refers to a view (logic) to display multiple instances of a table in the database. We have already discussed the basics of List View in List 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 view with few lines only. This is where Object Oriented Programming comes into impact. 

Django List View – Function Based Views

Illustration of How to create and use List view using an Example. Consider a project named neveropen having an app named Lazyroar. 

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 Lazyroar/models.py, 

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 Lazyroar.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/Lazyroar/Lazyroarmodel/ 

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

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

Create a template in templates/Lazyroar/Lazyroarmodel_list.html, 

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

Manipulate Queryset in ListView

By default ListView will display all instances of a table in the order they were created. If one wants to modify the sequence of these instances or the ordering, get_queryset method need to be overridden. 
In Lazyroar/views.py, 

Now check, if the order of instances has been reversed. 

This way one can modify the entire queryset in any manner possible.