ViewSets and routers in Django

Introduction

ViewSets and routers help you write less code to handle common web actions like showing, adding, or changing data.

When you want to create a simple API to list, create, update, or delete items.

When you want to avoid writing separate functions for each action in your web app.

When you want your URLs to be created automatically for common actions.

When you want to keep your code clean and organized by grouping related actions.

When you want to quickly build REST APIs without repeating code.

Syntax

Django

from rest_framework import viewsets
from rest_framework.routers import DefaultRouter

class MyModelViewSet(viewsets.ModelViewSet):
    queryset = MyModel.objects.all()
    serializer_class = MyModelSerializer

router = DefaultRouter()
router.register(r'mymodels', MyModelViewSet)

urlpatterns = router.urls

ViewSet: A class that groups common actions like list, create, update, delete.

Router: Automatically creates URL patterns for the ViewSet actions.

Examples

This ViewSet handles all CRUD actions for books.

Django

class BookViewSet(viewsets.ModelViewSet):
    queryset = Book.objects.all()
    serializer_class = BookSerializer

This router creates URLs like /books/, /books/{id}/ automatically.

Django

router = DefaultRouter()
router.register(r'books', BookViewSet)

urlpatterns = router.urls

This ViewSet only allows reading data (list and retrieve), no changes.

Django

class ReadOnlyBookViewSet(viewsets.ReadOnlyModelViewSet):
    queryset = Book.objects.all()
    serializer_class = BookSerializer

Sample Program

This example shows a full setup for a simple API to manage fruits. You can list all fruits, add new ones, update, or delete them using the URLs created automatically.

Django

from django.urls import path, include
from rest_framework import viewsets
from rest_framework.routers import DefaultRouter
from rest_framework.serializers import ModelSerializer
from django.db import models

# Simple model
class Fruit(models.Model):
    name = models.CharField(max_length=100)

# Serializer for Fruit
class FruitSerializer(ModelSerializer):
    class Meta:
        model = Fruit
        fields = ['id', 'name']

# ViewSet for Fruit
class FruitViewSet(viewsets.ModelViewSet):
    queryset = Fruit.objects.all()
    serializer_class = FruitSerializer

# Router setup
router = DefaultRouter()
router.register(r'fruits', FruitViewSet)

# URL patterns
urlpatterns = [
    path('', include(router.urls)),
]

# Explanation:
# This code creates a Fruit model, serializer, and a ViewSet that handles all actions.
# The router automatically creates URLs like /fruits/ and /fruits/{id}/ for listing and detail.

Important Notes

Routers save time by creating URLs for you, so you don't write them manually.

ViewSets group related actions, making your code cleaner and easier to read.

You can customize which actions are allowed by choosing different ViewSet classes.

Summary

ViewSets group common web actions like list, create, update, and delete.

Routers automatically create URLs for these actions, saving you from writing URL code.

This combination helps you build clean and simple APIs quickly.

Practice

1. What is the main purpose of using ViewSets in Django REST Framework?

easy

A. To group common web actions like list, create, update, and delete in one class

B. To define database models for the API

C. To write custom HTML templates for views

D. To handle user authentication manually

Solution

1. Step 1: Understand what ViewSets do

   ViewSets group common actions such as list, create, update, and delete into one class to simplify API views.

2. Step 2: Compare with other options

   Options B, C, and D describe unrelated tasks: models, templates, and authentication, which are not the main purpose of ViewSets.

3. Final Answer:

   To group common web actions like list, create, update, and delete in one class -> Option A

4. Quick Check:

   ViewSets group actions = A [OK]

Hint: ViewSets bundle common API actions together [OK]

Common Mistakes:

• Confusing ViewSets with models
• Thinking ViewSets handle templates
• Assuming ViewSets manage authentication

2. Which of the following is the correct way to register a ViewSet with a router in Django REST Framework?

easy

A. router.attach('items', ItemViewSet)

B. router.add('items', ItemViewSet)

C. router.register('items', ItemViewSet)

D. router.include('items', ItemViewSet)

Solution

1. Step 1: Recall the router method to register ViewSets

   The correct method to register a ViewSet with a router is register().

2. Step 2: Verify method names

   Methods like add(), include(), and attach() do not exist on routers for this purpose.

3. Final Answer:

   router.register('items', ItemViewSet) -> Option C

4. Quick Check:

   Use register() to add ViewSets to routers [OK]

Hint: Use router.register() to add ViewSets [OK]

Common Mistakes:

• Using non-existent router methods like add or include
• Confusing router registration with URL inclusion
• Forgetting to pass the ViewSet class

3. Given this code snippet, what URL patterns will be automatically created by the router?

from rest_framework import routers

router = routers.DefaultRouter()
router.register('books', BookViewSet)

medium

A. /books/list/ for list, /books/create/ for create

B. /books/viewset/ for all actions

C. /books/all/ for all actions

D. /books/ for list and create, /books/{pk}/ for retrieve, update, delete

Solution

1. Step 1: Understand DefaultRouter URL patterns

   DefaultRouter creates URLs like /books/ for listing and creating, and /books/{pk}/ for retrieve, update, and delete actions.

2. Step 2: Compare with other options

   Options A, C, and D use incorrect URL paths that are not generated by DefaultRouter automatically.

3. Final Answer:

   /books/ for list and create, /books/{pk}/ for retrieve, update, delete -> Option D

4. Quick Check:

   DefaultRouter creates standard REST URLs = B [OK]

Hint: DefaultRouter creates /resource/ and /resource/{id}/ URLs [OK]

Common Mistakes:

• Expecting custom URL suffixes like /list or /create
• Not knowing DefaultRouter auto-generates URLs
• Confusing URL patterns with manual URL configs

4. Identify the error in this router registration code:

from rest_framework import routers

router = routers.DefaultRouter()
router.register('authors', authorsViewSet)

medium

A. The ViewSet class name should be capitalized as AuthorsViewSet

B. The router should be SimpleRouter, not DefaultRouter

C. The register method requires a third argument for basename

D. The URL prefix 'authors' is invalid

Solution

1. Step 1: Check the ViewSet class name

   Python class names should be capitalized. 'authorsViewSet' is likely a typo and should be 'AuthorsViewSet'.

2. Step 2: Validate other options

   DefaultRouter is valid here, basename is optional if ViewSet has queryset, and 'authors' is a valid URL prefix.

3. Final Answer:

   The ViewSet class name should be capitalized as AuthorsViewSet -> Option A

4. Quick Check:

   Class names must be capitalized = A [OK]

Hint: Class names must start with uppercase letter [OK]

Common Mistakes:

• Using lowercase for class names
• Thinking basename is always required
• Confusing router types unnecessarily

5. You want to create a router that registers two ViewSets: ProductViewSet and CategoryViewSet. You also want to customize the basename for CategoryViewSet because it has no queryset attribute. Which code snippet correctly does this?

hard

A. router.register('products', ProductViewSet)
router.register('categories', CategoryViewSet)

B. router.register('products', ProductViewSet)
router.register('categories', CategoryViewSet, basename='category')

C. router.register('products', ProductViewSet, basename='product')
router.register('categories', CategoryViewSet)

D. router.register('products', ProductViewSet, basename='products')
router.register('categories', CategoryViewSet, basename=CategoryViewSet)

Solution

1. Step 1: Understand basename usage

   If a ViewSet lacks a queryset attribute, you must provide a basename when registering it with the router.

2. Step 2: Check the code snippets

   router.register('products', ProductViewSet) router.register('categories', CategoryViewSet, basename='category') correctly registers ProductViewSet without basename (assuming it has queryset) and CategoryViewSet with basename='category'. Other options either omit basename or misuse it.

3. Final Answer:

   router.register('products', ProductViewSet) router.register('categories', CategoryViewSet, basename='category') -> Option B

4. Quick Check:

   Provide basename if no queryset = C [OK]

Hint: Add basename if ViewSet has no queryset [OK]

Common Mistakes:

• Omitting basename for ViewSets without queryset
• Using wrong basename strings
• Adding basename unnecessarily