ViewSets and routers in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this ViewSet router URL pattern?

Given the following Django REST Framework router and ViewSet, what URL pattern will be registered for the 'list' action?

Django

from rest_framework import routers, viewsets
from django.urls import path, include

class BookViewSet(viewsets.ViewSet):
    def list(self, request):
        pass

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

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

A /book/list/ mapped to BookViewSet list action

B /book/ mapped to BookViewSet list action

C /books/ mapped to BookViewSet list action

D /books/list/ mapped to BookViewSet list action

💡 Hint

Remember how DefaultRouter registers routes for ViewSets using the basename and prefix.

The DefaultRouter registers the 'list' action at the prefix path, so 'books/' is the correct URL for the list action.

❓ state_output

intermediate

What is the HTTP method for the 'create' action in a ViewSet?

In Django REST Framework, which HTTP method triggers the 'create' action in a ViewSet when using a router?

A GET

B POST

C PUT

D DELETE

💡 Hint

Think about which HTTP method is used to add new data.

The 'create' action corresponds to the POST HTTP method to add new resources.

📝 Syntax

advanced

Which option correctly registers a ViewSet with a router for nested routes?

You want to register a nested route for comments under posts using routers in Django REST Framework. Which code snippet correctly does this?

A

router.register(r'posts', PostViewSet)
nested_router = routers.NestedDefaultRouter(router, r'posts', lookup='post')
nested_router.register(r'comments', CommentViewSet, basename='post-comments')

B router.register(r'posts/(?P<post_pk>[^/.]+)/comments', CommentViewSet, basename='post-comments')

C

router.register(r'posts', PostViewSet)
router.register(r'posts/comments', CommentViewSet)

D

router.register(r'posts', PostViewSet)
router.register(r'comments', CommentViewSet)

💡 Hint

Nested routes require a special nested router, not just string patterns.

Option A uses NestedDefaultRouter to properly create nested routes with lookup fields.

🔧 Debug

advanced

Why does this ViewSet raise a 405 Method Not Allowed error?

Consider this ViewSet: class ArticleViewSet(viewsets.ViewSet): def retrieve(self, request, pk=None): return Response({'id': pk}) router.register(r'articles', ArticleViewSet) Why does a GET request to /articles/ return 405 Method Not Allowed?

A Because the basename is missing in router.register

B Because 'retrieve' method is missing the 'self' parameter

C Because the router is not included in urlpatterns

D Because 'list' method is not defined, so GET on /articles/ is not allowed

💡 Hint

Check which actions correspond to which URLs and HTTP methods.

GET on /articles/ calls the 'list' action, which is not defined, so 405 is returned.

🧠 Conceptual

expert

What is the main advantage of using routers with ViewSets in Django REST Framework?

Why do developers prefer using routers with ViewSets instead of manually defining URL patterns for each view?

A Routers automatically generate standard RESTful URL patterns and reduce repetitive code

B Routers improve database query performance by caching queries

C Routers allow using class-based views without serializers

D Routers enable asynchronous request handling by default

💡 Hint

Think about how routers help with URL management and code simplicity.

Routers simplify URL routing by automatically creating RESTful routes for ViewSets, reducing manual URL definitions.

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