Prompt Title: Django viewset object permissions.

Sure, here's an example of how to implement object-level permissions in a Django viewset:

Let's say you have a model called Book:

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# models.py
from django.db import models

class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.CharField(max_length=100)
    published_date = models.DateField()
    is_published = models.BooleanField(default=False)

And you have a viewset for this model:

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# views.py
from rest_framework import viewsets
from .serializers import BookSerializer
from .models import Book

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

Now let's say you want to restrict access to certain books based on their is_published status. You can define a permission class that checks this:

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# permissions.py
from rest_framework import permissions

class IsPublishedOrAdmin(permissions.BasePermission):
    def has_object_permission(self, request, view, obj):
        # allow admins to access all objects
        if request.user.is_staff:
            return True

        # allow non-admins to access published objects only
        return obj.is_published

Finally, you can apply this permission class to your viewset:

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# views.py
from rest_framework import viewsets
from .serializers import BookSerializer
from .models import Book
from .permissions import IsPublishedOrAdmin

class BookViewSet(viewsets.ModelViewSet):
    queryset = Book.objects.all()
    serializer_class = BookSerializer
    permission_classes = [IsPublishedOrAdmin]

Now when a user tries to access a book that is not published, they will receive a 403 Forbidden error unless they are an admin.