Django Cbv Patterns

Django Class-Based Views

Master Django Class-Based Views for building modular, reusable view logic with proper separation of concerns.

Generic Views

Use Django's built-in generic views for common patterns.

from django.views.generic import ListView, DetailView, CreateView, UpdateView, DeleteView
from django.urls import reverse_lazy

class PostListView(ListView):
    model = Post
    template_name = 'posts/list.html'
    context_object_name = 'posts'
    paginate_by = 10
    ordering = ['-created_at']

    def get_queryset(self):
        queryset = super().get_queryset()
        # Only show published posts
        return queryset.filter(published=True).select_related('author')

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['total_posts'] = self.get_queryset().count()
        return context

class PostDetailView(DetailView):
    model = Post
    template_name = 'posts/detail.html'
    context_object_name = 'post'

    def get_queryset(self):
        return super().get_queryset().select_related('author').prefetch_related('comments')

class PostCreateView(CreateView):
    model = Post
    fields = ['title', 'content', 'published']
    template_name = 'posts/create.html'
    success_url = reverse_lazy('post-list')

    def form_valid(self, form):
        form.instance.author = self.request.user
        return super().form_valid(form)

class PostUpdateView(UpdateView):
    model = Post
    fields = ['title', 'content', 'published']
    template_name = 'posts/update.html'

    def get_success_url(self):
        return reverse_lazy('post-detail', kwargs={'pk': self.object.pk})

class PostDeleteView(DeleteView):
    model = Post
    template_name = 'posts/confirm_delete.html'
    success_url = reverse_lazy('post-list')

Built-in Mixins

Leverage Django's built-in mixins for common functionality.

from django.contrib.auth.mixins import LoginRequiredMixin, UserPassesTestMixin, PermissionRequiredMixin
from django.views.generic import CreateView, UpdateView

class PostCreateView(LoginRequiredMixin, CreateView):
    model = Post
    fields = ['title', 'content']
    login_url = '/login/'
    redirect_field_name = 'next'

class PostUpdateView(LoginRequiredMixin, UserPassesTestMixin, UpdateView):
    model = Post
    fields = ['title', 'content']

    def test_func(self):
        post = self.get_object()
        return self.request.user == post.author

    def handle_no_permission(self):
        # Custom handling when test fails
        messages.error(self.request, 'You can only edit your own posts')
        return redirect('post-list')

class AdminPostListView(PermissionRequiredMixin, ListView):
    model = Post
    permission_required = 'posts.view_post'
    raise_exception = True  # Return 403 instead of redirect

Custom Mixins

Create reusable mixins for common patterns.

from django.views.generic import View
from django.shortcuts import redirect
from django.contrib import messages

class AuthorRequiredMixin:
    """Ensure the current user is the object's author."""

    def dispatch(self, request, *args, **kwargs):
        obj = self.get_object()
        if obj.author != request.user:
            messages.error(request, 'You do not have permission')
            return redirect('post-list')
        return super().dispatch(request, *args, **kwargs)

class FormMessageMixin:
    """Add success messages to form views."""
    success_message = ''

    def form_valid(self, form):
        response = super().form_valid(form)
        if self.success_message:
            messages.success(self.request, self.success_message)
        return response

class AjaxableResponseMixin:
    """Handle AJAX requests differently."""

    def form_valid(self, form):
        if self.request.is_ajax():
            data = {
                'pk': form.instance.pk,
                'success': True
            }
            return JsonResponse(data)
        return super().form_valid(form)

    def form_invalid(self, form):
        if self.request.is_ajax():
            return JsonResponse(form.errors, status=400)
        return super().form_invalid(form)

# Usage
class PostUpdateView(LoginRequiredMixin, AuthorRequiredMixin, FormMessageMixin, UpdateView):
    model = Post
    fields = ['title', 'content']
    success_message = 'Post updated successfully'

Method Resolution Order (MRO)

Understand how Django resolves methods in CBVs.

# MRO matters! Order from left to right
class PostUpdateView(
    LoginRequiredMixin,      # Check login first
    AuthorRequiredMixin,     # Then check authorship
    FormMessageMixin,        # Add messages
    UpdateView               # Base view last
):
    model = Post
    fields = ['title', 'content']

# View the MRO
print(PostUpdateView.__mro__)

# Bad example - wrong order
class BadPostUpdateView(
    UpdateView,              # Base view first - wrong!
    LoginRequiredMixin,
    AuthorRequiredMixin
):
    pass  # Mixins won't work correctly

# Override dispatch to control flow
class CustomView(LoginRequiredMixin, UpdateView):
    def dispatch(self, request, *args, **kwargs):
        # Custom logic before any other processing
        if not request.user.is_verified:
            return redirect('verify-email')
        return super().dispatch(request, *args, **kwargs)

Form Handling in CBVs

Advanced form handling patterns.

from django.views.generic.edit import FormView
from django.contrib import messages

class ContactFormView(FormView):
    template_name = 'contact.html'
    form_class = ContactForm
    success_url = '/thanks/'

    def get_form_kwargs(self):
        """Pass request to form."""
        kwargs = super().get_form_kwargs()
        kwargs['request'] = self.request
        return kwargs

    def get_initial(self):
        """Pre-populate form."""
        initial = super().get_initial()
        if self.request.user.is_authenticated:
            initial['email'] = self.request.user.email
            initial['name'] = self.request.user.name
        return initial

    def form_valid(self, form):
        form.send_email()
        messages.success(self.request, 'Message sent!')
        return super().form_valid(form)

    def form_invalid(self, form):
        messages.error(self.request, 'Please correct the errors')
        return super().form_invalid(form)

# Multiple forms in one view
class ProfileUpdateView(LoginRequiredMixin, TemplateView):
    template_name = 'profile.html'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        if 'user_form' not in context:
            context['user_form'] = UserForm(instance=self.request.user)
        if 'profile_form' not in context:
            context['profile_form'] = ProfileForm(instance=self.request.user.profile)
        return context

    def post(self, request, *args, **kwargs):
        user_form = UserForm(request.POST, instance=request.user)
        profile_form = ProfileForm(request.POST, instance=request.user.profile)

        if user_form.is_valid() and profile_form.is_valid():
            user_form.save()
            profile_form.save()
            messages.success(request, 'Profile updated')
            return redirect('profile')

        return self.render_to_response(
            self.get_context_data(user_form=user_form, profile_form=profile_form)
        )

When to Use CBVs vs FBVs

Guidelines for choosing between class-based and function-based views.

# Use CBVs for:
# 1. Standard CRUD operations
class PostListView(ListView):
    model = Post

# 2. Reusable view logic
class OwnerRequiredMixin:
    def get_queryset(self):
        return super().get_queryset().filter(owner=self.request.user)

# 3. Multiple similar views
class UserPostListView(OwnerRequiredMixin, ListView):
    model = Post

class UserDraftListView(OwnerRequiredMixin, ListView):
    model = Post
    queryset = Post.objects.filter(published=False)

# Use FBVs for:
# 1. Simple one-off views
def simple_view(request):
    return render(request, 'simple.html')

# 2. Complex custom logic that doesn't fit CBV patterns
def complex_workflow(request):
    if request.method == 'POST':
        # Complex multi-step logic
        step = request.POST.get('step')
        if step == '1':
            # Process step 1
            pass
        elif step == '2':
            # Process step 2
            pass
    return render(request, 'workflow.html')

# 3. Views that handle multiple models in non-standard ways
def dashboard(request):
    posts = Post.objects.filter(author=request.user)
    comments = Comment.objects.filter(post__author=request.user)
    analytics = calculate_analytics(request.user)
    return render(request, 'dashboard.html', {
        'posts': posts,
        'comments': comments,
        'analytics': analytics
    })

Testing CBVs

Comprehensive testing strategies for class-based views.

from django.test import TestCase, RequestFactory
from django.contrib.auth.models import User, AnonymousUser

class PostListViewTest(TestCase):
    def setUp(self):
        self.factory = RequestFactory()
        self.user = User.objects.create_user(
            username='testuser',
            password='testpass'
        )

    def test_list_view(self):
        request = self.factory.get('/posts/')
        request.user = self.user
        response = PostListView.as_view()(request)
        self.assertEqual(response.status_code, 200)

    def test_queryset_only_published(self):
        Post.objects.create(title='Published', author=self.user, published=True)
        Post.objects.create(title='Draft', author=self.user, published=False)

        request = self.factory.get('/posts/')
        request.user = self.user
        response = PostListView.as_view()(request)
        self.assertEqual(len(response.context_data['posts']), 1)

    def test_login_required(self):
        request = self.factory.get('/posts/create/')
        request.user = AnonymousUser()
        response = PostCreateView.as_view()(request)
        self.assertEqual(response.status_code, 302)  # Redirect to login

    def test_author_required(self):
        other_user = User.objects.create_user('other', password='pass')
        post = Post.objects.create(title='Test', author=other_user)

        request = self.factory.get(f'/posts/{post.pk}/edit/')
        request.user = self.user
        response = PostUpdateView.as_view()(request, pk=post.pk)
        self.assertEqual(response.status_code, 302)  # Redirect denied

Advanced Patterns

Complex CBV patterns for production applications.

# Filtering with GET parameters
class PostFilterView(ListView):
    model = Post
    paginate_by = 20

    def get_queryset(self):
        queryset = super().get_queryset()
        author = self.request.GET.get('author')
        published = self.request.GET.get('published')

        if author:
            queryset = queryset.filter(author__name__icontains=author)
        if published is not None:
            queryset = queryset.filter(published=published == 'true')

        return queryset

# Dynamic template selection
class PostDetailView(DetailView):
    model = Post

    def get_template_names(self):
        if self.request.user == self.object.author:
            return ['posts/detail_owner.html']
        return ['posts/detail.html']

# JSON response view
from django.http import JsonResponse

class PostJSONView(DetailView):
    model = Post

    def render_to_response(self, context, **response_kwargs):
        return JsonResponse({
            'id': self.object.id,
            'title': self.object.title,
            'content': self.object.content,
            'author': self.object.author.name
        })

# Conditional form fields
class PostCreateView(CreateView):
    model = Post
    template_name = 'posts/create.html'

    def get_form_class(self):
        if self.request.user.is_staff:
            return AdminPostForm
        return UserPostForm

# Multiple object types
from django.views.generic import TemplateView

class SearchView(TemplateView):
    template_name = 'search.html'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        query = self.request.GET.get('q', '')

        if query:
            context['posts'] = Post.objects.filter(title__icontains=query)
            context['users'] = User.objects.filter(name__icontains=query)
            context['query'] = query

        return context

Pagination in CBVs

Implement sophisticated pagination patterns.

from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
from django.views.generic import ListView

class PostListView(ListView):
    model = Post
    paginate_by = 20
    paginate_orphans = 5  # Avoid last page with few items

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)

        # Add custom pagination data
        paginator = context['paginator']
        page_obj = context['page_object']

        # Calculate page range for display
        index = page_obj.number - 1
        max_index = len(paginator.page_range)
        start_index = index - 3 if index >= 3 else 0
        end_index = index + 4 if index <= max_index - 4 else max_index

        context['page_range'] = list(paginator.page_range)[start_index:end_index]
        context['total_pages'] = paginator.num_pages

        return context

# AJAX pagination
class AjaxPostListView(ListView):
    model = Post
    paginate_by = 10
    template_name = 'posts/list.html'

    def get_template_names(self):
        if self.request.is_ajax():
            return ['posts/partials/post_list.html']
        return [self.template_name]

    def render_to_response(self, context, **response_kwargs):
        if self.request.is_ajax():
            from django.http import JsonResponse
            posts = [
                {
                    'id': post.id,
                    'title': post.title,
                    'author': post.author.name
                }
                for post in context['object_list']
            ]
            return JsonResponse({
                'posts': posts,
                'has_next': context['page_obj'].has_next(),
                'page': context['page_obj'].number
            })
        return super().render_to_response(context, **response_kwargs)

# Infinite scroll pagination
class InfiniteScrollListView(ListView):
    model = Post
    paginate_by = 20

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['is_infinite_scroll'] = True
        return context

Context Data Manipulation

Master advanced context manipulation techniques.

class PostDetailView(DetailView):
    model = Post

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)

        # Add related data
        post = self.object
        context['related_posts'] = Post.objects.filter(
            category=post.category
        ).exclude(id=post.id)[:5]

        # Add user-specific data
        if self.request.user.is_authenticated:
            context['has_liked'] = post.likes.filter(
                user=self.request.user
            ).exists()
            context['is_bookmarked'] = post.bookmarks.filter(
                user=self.request.user
            ).exists()

        # Add computed data
        context['reading_time'] = post.calculate_reading_time()
        context['share_url'] = self.request.build_absolute_uri()

        return context

# Multiple context mixins
class AnalyticsMixin:
    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['analytics_enabled'] = True
        context['tracking_id'] = settings.ANALYTICS_ID
        return context

class BreadcrumbMixin:
    breadcrumbs = []

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['breadcrumbs'] = self.get_breadcrumbs()
        return context

    def get_breadcrumbs(self):
        return self.breadcrumbs

class PostDetailView(AnalyticsMixin, BreadcrumbMixin, DetailView):
    model = Post
    breadcrumbs = [
        ('Home', '/'),
        ('Posts', '/posts/'),
    ]

    def get_breadcrumbs(self):
        breadcrumbs = super().get_breadcrumbs()
        breadcrumbs.append((self.object.title, None))
        return breadcrumbs

Method Override Patterns

Override specific methods for fine-grained control.

class PostCreateView(CreateView):
    model = Post
    fields = ['title', 'content', 'category']

    # Control initial form data
    def get_initial(self):
        initial = super().get_initial()
        if self.request.user.is_authenticated:
            initial['author'] = self.request.user
        return initial

    # Control form kwargs
    def get_form_kwargs(self):
        kwargs = super().get_form_kwargs()
        kwargs['user'] = self.request.user
        kwargs['categories'] = Category.objects.filter(active=True)
        return kwargs

    # Control form class selection
    def get_form_class(self):
        if self.request.user.is_staff:
            return AdminPostForm
        return PostForm

    # Control success URL dynamically
    def get_success_url(self):
        if 'save_and_add' in self.request.POST:
            return reverse('post-create')
        return reverse('post-detail', kwargs={'pk': self.object.pk})

    # Customize form validation
    def form_valid(self, form):
        form.instance.author = self.request.user
        form.instance.ip_address = self.request.META.get('REMOTE_ADDR')

        # Additional validation
        if form.instance.published and not form.instance.content:
            form.add_error('content', 'Published posts must have content')
            return self.form_invalid(form)

        response = super().form_valid(form)

        # Post-save actions
        messages.success(self.request, 'Post created successfully')

        return response

    # Customize form error handling
    def form_invalid(self, form):
        messages.error(self.request, 'Please correct the errors below')
        return super().form_invalid(form)

# Override get_object for custom logic
class PostUpdateView(UpdateView):
    model = Post

    def get_object(self, queryset=None):
        obj = super().get_object(queryset)

        # Track view
        obj.views += 1
        obj.save(update_fields=['views'])

        # Check permissions
        if obj.author != self.request.user and not self.request.user.is_staff:
            raise PermissionDenied('You can only edit your own posts')

        return obj

    def get_queryset(self):
        queryset = super().get_queryset()

        # Filter based on user
        if not self.request.user.is_staff:
            queryset = queryset.filter(author=self.request.user)

        # Optimize queries
        queryset = queryset.select_related('author', 'category')

        return queryset

Advanced Mixin Composition

Build complex functionality through mixin composition.

from django.contrib import messages
from django.shortcuts import redirect
from django.core.exceptions import PermissionDenied

class SetHeadlineMixin:
    """Add a headline to the context."""
    headline = None

    def get_headline(self):
        return self.headline

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['headline'] = self.get_headline()
        return context

class SetButtonTextMixin:
    """Add button text to the context."""
    button_text = 'Submit'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['button_text'] = self.button_text
        return context

class FormValidMessageMixin:
    """Display success message after form submission."""
    success_message = 'Form submitted successfully'

    def form_valid(self, form):
        response = super().form_valid(form)
        messages.success(self.request, self.get_success_message(form))
        return response

    def get_success_message(self, form):
        return self.success_message

class DeleteConfirmMixin:
    """Require confirmation before deletion."""
    def delete(self, request, *args, **kwargs):
        if not request.POST.get('confirm'):
            messages.warning(request, 'Please confirm deletion')
            return redirect(self.get_success_url())

        messages.success(request, 'Item deleted successfully')
        return super().delete(request, *args, **kwargs)

class StaffRequiredMixin:
    """Require staff user."""
    def dispatch(self, request, *args, **kwargs):
        if not request.user.is_staff:
            raise PermissionDenied
        return super().dispatch(request, *args, **kwargs)

class AuditMixin:
    """Track creation and updates."""
    def form_valid(self, form):
        if not form.instance.pk:
            form.instance.created_by = self.request.user
        form.instance.updated_by = self.request.user
        return super().form_valid(form)

# Compose multiple mixins
class PostCreateView(
    LoginRequiredMixin,
    SetHeadlineMixin,
    SetButtonTextMixin,
    FormValidMessageMixin,
    AuditMixin,
    CreateView
):
    model = Post
    fields = ['title', 'content']
    headline = 'Create New Post'
    button_text = 'Create Post'
    success_message = 'Post created successfully!'

Search and Filter Views

Implement advanced search and filtering.

from django.db.models import Q
from django.views.generic import ListView

class PostSearchView(ListView):
    model = Post
    template_name = 'posts/search.html'
    paginate_by = 20

    def get_queryset(self):
        queryset = super().get_queryset()
        query = self.request.GET.get('q')

        if query:
            queryset = queryset.filter(
                Q(title__icontains=query) |
                Q(content__icontains=query) |
                Q(author__name__icontains=query)
            )

        return queryset

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['query'] = self.request.GET.get('q', '')
        context['result_count'] = context['paginator'].count
        return context

class PostFilterView(ListView):
    model = Post
    template_name = 'posts/filter.html'
    paginate_by = 20

    def get_queryset(self):
        queryset = super().get_queryset()

        # Category filter
        category = self.request.GET.get('category')
        if category:
            queryset = queryset.filter(category_id=category)

        # Author filter
        author = self.request.GET.get('author')
        if author:
            queryset = queryset.filter(author_id=author)

        # Date range filter
        date_from = self.request.GET.get('date_from')
        date_to = self.request.GET.get('date_to')
        if date_from:
            queryset = queryset.filter(created_at__gte=date_from)
        if date_to:
            queryset = queryset.filter(created_at__lte=date_to)

        # Published filter
        published = self.request.GET.get('published')
        if published is not None:
            queryset = queryset.filter(published=published == 'true')

        # Sorting
        sort = self.request.GET.get('sort', '-created_at')
        allowed_sorts = ['created_at', '-created_at', 'title', '-title', 'views', '-views']
        if sort in allowed_sorts:
            queryset = queryset.order_by(sort)

        return queryset.select_related('author', 'category')

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['categories'] = Category.objects.all()
        context['authors'] = User.objects.filter(posts__isnull=False).distinct()
        context['filters'] = self.request.GET
        return context

File Upload Views

Handle file uploads with CBVs.

from django.views.generic.edit import FormView
from django.core.files.storage import default_storage

class FileUploadView(FormView):
    template_name = 'upload.html'
    form_class = FileUploadForm
    success_url = '/success/'

    def form_valid(self, form):
        file = form.cleaned_data['file']

        # Save file
        filename = default_storage.save(f'uploads/{file.name}', file)

        # Process file
        self.process_file(filename)

        messages.success(self.request, f'File {file.name} uploaded successfully')
        return super().form_valid(form)

    def process_file(self, filename):
        # Custom file processing logic
        pass

class MultipleFileUploadView(FormView):
    template_name = 'upload_multiple.html'
    form_class = MultipleFileUploadForm
    success_url = '/success/'

    def form_valid(self, form):
        files = self.request.FILES.getlist('files')

        for file in files:
            # Validate file
            if file.size > 10 * 1024 * 1024:  # 10MB limit
                form.add_error('files', f'{file.name} exceeds size limit')
                return self.form_invalid(form)

            # Save file
            filename = default_storage.save(f'uploads/{file.name}', file)

            # Create database record
            FileUpload.objects.create(
                filename=filename,
                original_name=file.name,
                size=file.size,
                uploaded_by=self.request.user
            )

        messages.success(self.request, f'{len(files)} files uploaded successfully')
        return super().form_valid(form)

class ImageUploadView(CreateView):
    model = Image
    fields = ['title', 'image', 'description']
    template_name = 'images/upload.html'

    def form_valid(self, form):
        form.instance.uploaded_by = self.request.user

        # Validate image
        image = form.cleaned_data['image']
        if image.size > 5 * 1024 * 1024:  # 5MB
            form.add_error('image', 'Image too large')
            return self.form_invalid(form)

        # Process image (resize, thumbnail, etc.)
        form.instance.thumbnail = self.create_thumbnail(image)

        return super().form_valid(form)

    def create_thumbnail(self, image):
        # Thumbnail creation logic
        pass

Performance Optimization

Optimize CBVs for better performance.

class OptimizedPostListView(ListView):
    model = Post
    paginate_by = 20

    def get_queryset(self):
        return Post.objects.select_related(
            'author'
        ).prefetch_related(
            'comments'
        ).only(
            'id', 'title', 'created_at', 'author__name'
        ).filter(
            published=True
        )

# Caching
from django.views.decorators.cache import cache_page
from django.utils.decorators import method_decorator

@method_decorator(cache_page(60 * 15), name='dispatch')
class CachedPostListView(ListView):
    model = Post

# Conditional caching based on user
class SmartCachedView(ListView):
    model = Post

    @method_decorator(cache_page(60 * 15))
    def dispatch(self, request, *args, **kwargs):
        if request.user.is_authenticated:
            # Don't cache for authenticated users
            return super().dispatch(request, *args, **kwargs)
        return super().dispatch(request, *args, **kwargs)

# ETags for caching
from django.views.decorators.http import condition

def latest_post(request, *args, **kwargs):
    return Post.objects.latest('updated_at').updated_at

def post_etag(request, *args, **kwargs):
    return str(Post.objects.latest('updated_at').updated_at.timestamp())

class PostListView(ListView):
    model = Post

    @method_decorator(condition(etag_func=post_etag, last_modified_func=latest_post))
    def dispatch(self, *args, **kwargs):
        return super().dispatch(*args, **kwargs)

When to Use This Skill

Use django-cbv-patterns when building modern, production-ready applications that require advanced patterns, best practices, and optimal performance.

API Views with CBVs

Build API endpoints using CBVs without DRF.

from django.http import JsonResponse
from django.views.generic import View
from django.views.decorators.csrf import csrf_exempt
from django.utils.decorators import method_decorator
import json

@method_decorator(csrf_exempt, name='dispatch')
class PostAPIView(View):
    def get(self, request, *args, **kwargs):
        posts = Post.objects.filter(published=True).values(
            'id', 'title', 'content', 'author__name'
        )
        return JsonResponse(list(posts), safe=False)

    def post(self, request, *args, **kwargs):
        try:
            data = json.loads(request.body)
            post = Post.objects.create(
                title=data['title'],
                content=data['content'],
                author=request.user
            )
            return JsonResponse({
                'id': post.id,
                'title': post.title,
                'message': 'Post created successfully'
            }, status=201)
        except Exception as e:
            return JsonResponse({'error': str(e)}, status=400)

class PostDetailAPIView(View):
    def get(self, request, pk, *args, **kwargs):
        try:
            post = Post.objects.select_related('author').get(pk=pk)
            return JsonResponse({
                'id': post.id,
                'title': post.title,
                'content': post.content,
                'author': post.author.name,
                'created_at': post.created_at.isoformat()
            })
        except Post.DoesNotExist:
            return JsonResponse({'error': 'Post not found'}, status=404)

    def put(self, request, pk, *args, **kwargs):
        try:
            post = Post.objects.get(pk=pk)
            data = json.loads(request.body)

            post.title = data.get('title', post.title)
            post.content = data.get('content', post.content)
            post.save()

            return JsonResponse({'message': 'Post updated successfully'})
        except Post.DoesNotExist:
            return JsonResponse({'error': 'Post not found'}, status=404)

    def delete(self, request, pk, *args, **kwargs):
        try:
            post = Post.objects.get(pk=pk)
            post.delete()
            return JsonResponse({'message': 'Post deleted successfully'})
        except Post.DoesNotExist:
            return JsonResponse({'error': 'Post not found'}, status=404)

Wizard and Multi-Step Forms

Implement multi-step form wizards with CBVs.

from django.views.generic import TemplateView
from django.shortcuts import redirect
from django.urls import reverse

class MultiStepFormMixin:
    """Mixin for multi-step form handling."""

    def get_step(self):
        return int(self.request.GET.get('step', 1))

    def get_session_key(self, step):
        return f'form_data_step_{step}'

    def save_step_data(self, step, data):
        self.request.session[self.get_session_key(step)] = data

    def get_step_data(self, step):
        return self.request.session.get(self.get_session_key(step), {})

    def clear_wizard_data(self):
        for key in list(self.request.session.keys()):
            if key.startswith('form_data_step_'):
                del self.request.session[key]

class UserRegistrationWizard(MultiStepFormMixin, TemplateView):
    template_name = 'registration/wizard.html'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        step = self.get_step()

        if step == 1:
            context['form'] = UserBasicInfoForm(initial=self.get_step_data(1))
        elif step == 2:
            context['form'] = UserProfileForm(initial=self.get_step_data(2))
        elif step == 3:
            context['form'] = UserPreferencesForm(initial=self.get_step_data(3))

        context['step'] = step
        context['total_steps'] = 3
        return context

    def post(self, request, *args, **kwargs):
        step = self.get_step()

        if step == 1:
            form = UserBasicInfoForm(request.POST)
            if form.is_valid():
                self.save_step_data(1, form.cleaned_data)
                return redirect(f'{reverse("registration-wizard")}?step=2')

        elif step == 2:
            form = UserProfileForm(request.POST)
            if form.is_valid():
                self.save_step_data(2, form.cleaned_data)
                return redirect(f'{reverse("registration-wizard")}?step=3')

        elif step == 3:
            form = UserPreferencesForm(request.POST)
            if form.is_valid():
                self.save_step_data(3, form.cleaned_data)

                # Create user with all data
                self.create_user()
                self.clear_wizard_data()

                return redirect('registration-complete')

        return self.render_to_response(self.get_context_data(form=form))

    def create_user(self):
        data1 = self.get_step_data(1)
        data2 = self.get_step_data(2)
        data3 = self.get_step_data(3)

        user = User.objects.create_user(
            username=data1['username'],
            email=data1['email'],
            password=data1['password']
        )

        Profile.objects.create(
            user=user,
            bio=data2['bio'],
            avatar=data2['avatar']
        )

        Preferences.objects.create(
            user=user,
            notifications=data3['notifications'],
            privacy=data3['privacy']
        )

Redirect and Success URL Patterns

Master URL redirection strategies.

from django.urls import reverse, reverse_lazy
from django.views.generic import CreateView, UpdateView

class PostCreateView(CreateView):
    model = Post
    fields = ['title', 'content']

    # Static success URL
    success_url = reverse_lazy('post-list')

    # Dynamic success URL based on object
    def get_success_url(self):
        return reverse('post-detail', kwargs={'pk': self.object.pk})

class PostUpdateView(UpdateView):
    model = Post
    fields = ['title', 'content']

    # Success URL based on form submission button
    def get_success_url(self):
        if 'save_and_continue' in self.request.POST:
            return reverse('post-update', kwargs={'pk': self.object.pk})
        elif 'save_and_add' in self.request.POST:
            return reverse('post-create')
        else:
            return reverse('post-detail', kwargs={'pk': self.object.pk})

class FlexibleRedirectMixin:
    """Redirect to next parameter or default."""

    def get_success_url(self):
        next_url = self.request.GET.get('next') or self.request.POST.get('next')
        if next_url:
            return next_url
        return super().get_success_url()

class PostDeleteView(FlexibleRedirectMixin, DeleteView):
    model = Post
    success_url = reverse_lazy('post-list')

Template and Response Customization

Customize template selection and response rendering.

from django.views.generic import DetailView
from django.http import HttpResponse
from django.template.loader import render_to_string

class PostDetailView(DetailView):
    model = Post

    # Dynamic template selection
    def get_template_names(self):
        # Mobile template
        if self.request.user_agent.is_mobile:
            return ['posts/detail_mobile.html']

        # Owner template
        if self.request.user == self.object.author:
            return ['posts/detail_owner.html']

        # Default template
        return ['posts/detail.html']

class ExportMixin:
    """Add export functionality to views."""

    def render_to_response(self, context, **response_kwargs):
        export_format = self.request.GET.get('format')

        if export_format == 'pdf':
            return self.render_to_pdf(context)
        elif export_format == 'csv':
            return self.render_to_csv(context)
        elif export_format == 'json':
            return self.render_to_json(context)

        return super().render_to_response(context, **response_kwargs)

    def render_to_pdf(self, context):
        # PDF rendering logic
        html = render_to_string(self.template_name, context)
        # Convert to PDF
        return HttpResponse(pdf_content, content_type='application/pdf')

    def render_to_csv(self, context):
        import csv
        from io import StringIO

        output = StringIO()
        writer = csv.writer(output)

        # Write CSV data
        for obj in context['object_list']:
            writer.writerow([obj.id, obj.title, obj.author.name])

        response = HttpResponse(output.getvalue(), content_type='text/csv')
        response['Content-Disposition'] = 'attachment; filename="export.csv"'
        return response

    def render_to_json(self, context):
        from django.http import JsonResponse
        data = [
            {
                'id': obj.id,
                'title': obj.title,
                'author': obj.author.name
            }
            for obj in context['object_list']
        ]
        return JsonResponse(data, safe=False)

class PostListView(ExportMixin, ListView):
    model = Post

Advanced Testing Patterns

Write comprehensive tests for CBVs.

from django.test import TestCase, RequestFactory, Client
from django.contrib.auth.models import User, AnonymousUser
from django.urls import reverse

class PostViewTestCase(TestCase):
    def setUp(self):
        self.factory = RequestFactory()
        self.user = User.objects.create_user(
            username='testuser',
            password='testpass'
        )
        self.post = Post.objects.create(
            title='Test Post',
            author=self.user
        )

    def test_list_view_with_factory(self):
        """Test using RequestFactory."""
        request = self.factory.get('/posts/')
        request.user = self.user

        response = PostListView.as_view()(request)
        self.assertEqual(response.status_code, 200)

    def test_detail_view_with_client(self):
        """Test using Client."""
        client = Client()
        response = client.get(reverse('post-detail', kwargs={'pk': self.post.pk}))
        self.assertEqual(response.status_code, 200)
        self.assertContains(response, 'Test Post')

    def test_create_view_requires_login(self):
        """Test login requirement."""
        request = self.factory.get('/posts/create/')
        request.user = AnonymousUser()

        response = PostCreateView.as_view()(request)
        self.assertEqual(response.status_code, 302)  # Redirect to login

    def test_update_view_author_only(self):
        """Test author-only access."""
        other_user = User.objects.create_user('other', password='pass')
        request = self.factory.get(f'/posts/{self.post.pk}/edit/')
        request.user = other_user

        with self.assertRaises(PermissionDenied):
            PostUpdateView.as_view()(request, pk=self.post.pk)

    def test_context_data(self):
        """Test context data."""
        request = self.factory.get('/posts/')
        request.user = self.user

        view = PostListView()
        view.request = request
        view.object_list = Post.objects.all()

        context = view.get_context_data()
        self.assertIn('object_list', context)
        self.assertIn('view', context)

    def test_form_valid(self):
        """Test form submission."""
        data = {
            'title': 'New Post',
            'content': 'Test content'
        }
        request = self.factory.post('/posts/create/', data)
        request.user = self.user

        response = PostCreateView.as_view()(request)
        self.assertEqual(response.status_code, 302)  # Redirect after success
        self.assertTrue(Post.objects.filter(title='New Post').exists())

    def test_queryset_optimization(self):
        """Test query optimization.

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