mixins.py

class ObjectOwnerMixin:

    def get_queryset(self):
        return self.model.objects.filter(author=self.request.user)

views.py

from django.views.generic.edit import *
from .models import *
from .mixins import *


class App(ObjectOwnerMixin, UpdateView):
    template_name = 'test.html'
    success_url = '/'
    model = Posts
    fields = ['title', 'body', 'author']