Mixins in Django CBV

Mixins are small classes that add a single behavior to CBVs through multiple inheritance.

Built-in Mixins

LoginRequiredMixin

from django.contrib.auth.mixins import LoginRequiredMixin

class TaskListView(LoginRequiredMixin, ListView):
    model = Task
    login_url = '/login/'           # where to redirect
    redirect_field_name = 'next'    # parameter for return URL

PermissionRequiredMixin

from django.contrib.auth.mixins import PermissionRequiredMixin

class TaskCreateView(PermissionRequiredMixin, CreateView):
    model = Task
    permission_required = 'tasks.add_task'
    # or multiple permissions:
    permission_required = ['tasks.add_task', 'tasks.view_project']

UserPassesTestMixin

from django.contrib.auth.mixins import UserPassesTestMixin

class TaskEditView(UserPassesTestMixin, UpdateView):
    model = Task

    def test_func(self):
        task = self.get_object()
        return self.request.user == task.owner

Custom Mixin

class OwnerRequiredMixin:
    """Grants access only to the owner of the object."""

    def get_queryset(self):
        qs = super().get_queryset()
        return qs.filter(owner=self.request.user)

class TaskDetailView(LoginRequiredMixin, OwnerRequiredMixin, DetailView):
    model = Task

Inheritance Order (MRO)

# Correct order: mixins BEFORE the base class
class TaskView(LoginRequiredMixin, OwnerRequiredMixin, DetailView):
    ...

# INCORRECT: base class first
class TaskView(DetailView, LoginRequiredMixin):  # LoginRequired won't work
    ...

Python uses C3 linearization — super() calls the next class in the MRO from left to right.